Rework readme

[LexManos]

You can see what it looks like on github at https://github.com/MinecraftForge/MinecraftMavenizer/tree/readme-cleanup
Besides being more descriptive for consumers, this is also meant to document what files are actually generated.
Opened as a PR mainly cuz I suck at writing and I dont wanna have a bunch of 'fixed typo' builds.

I also reworked how the console entry point works:
If no task is specified, and the --help argument is not specified, it will default to the MavenTask.
This is because that's the only task people other then us really care about/should be using. So no need to specify it all the time.
If no task is specified, but the --help argument is, it will output the help info for all tasks:

Minecraft Mavenizer
Option      Description                                              
------      -----------                                              
--help      Displays this help message and exits                     
--maven     Generates a maven repository for Minecraft Artifacts     
--mcp       Generates a 'clean' sources jar from a MCPConfig pipeline
--mcp-data  Extracts a data file from a MCPConfig archive            

maven Task:
  Option                       Description                                        
  ------                       -----------                                        
  --artifact <String>          The artifact to attempt to generate, see the code  
                                 for supported formats (default: net.             
                                 minecraftforge:forge)                            
  --cache <File>               Directory to store data needed for this program    
                                 (default: cache)                                 
  --cache-only                 Only use caches, fail if any downloads need to     
                                 occur or if a task needs to do work              
  --client                     Shorthand for --artifact net.minecraft:client      
  --dependencies-only          Outputs the maven containing only the Gradle       
                                 Module and POM for the artifact's dependencies   
                                 without outputting the artifact itself           
  --fml                        Shorthand for --artifact net.minecraftforge:fmlonly
  --forge                      Shorthand for --artifact net.minecraftforge:forge  
  --global-auxiliary-variants  Declares sources and javadoc jars as global        
                                 variants, no matter the mapping version. This is 
                                 used to work around gradle/gradle#35065          
  --help                       Displays this help message and exits               
  --jdk-cache <File>           Directory to store jdks downloaded from the disoco 
                                 api (default: cache\jdks)                        
  --mapping-data               Shorthand for --artifact net.minecraft:mappings    
  --mappings <String>          Mappings to use for this artifact. Formatted as    
                                 channel:version (default: official)              
  --mc                         Shorthand for --artifact net.minecraft:joined      
  --offline                    Do not attempt to download anything (allows        
                                 offline operations, if possible)                 
  --output <File>              Root directory to generate the maven repository    
                                 (default: output)                                
  --parchment <String>         Version of parchment mappings to use, snapshots    
                                 are not supported                                
  --repository <String>        EXPERIMENTAL: URL of a foreign maven repository to 
                                 use for dependencies. The format is "name,url".  
                                 The name must not include any commas.            
  --server                     Shorthand for --artifact net.minecraft:server      
  --version [String]           The specific artifact version to generate          

mcp Task:
  Option                 Description                                            
  ------                 -----------                                            
  --artifact <String>    MCPConfig artifact coordinates                         
  --at [File]            Access Transformer config file to apply                
  --cache <File>         Directory to store data needed for this program        
                           (default: cache)                                     
  --help                 Displays this help message and exits                   
  --jdk-cache <File>     Directory to store jdks downloaded from the disoco api 
                           (default: cache\jdks)                                
  --mappings             Use to enable using official mappings                  
  --output <File>        File to output the final jar (default: output.jar)     
  --output-files <File>  File to output a JSON containing paths to extra files  
                           (default: files.json)                                
  --parchment <String>   Version of parchment mappings to use, snapshots are not
                           supported                                            
  --pipeline <String>    MCPConfig pipeline to run, typically                   
                           [client|server|joined] (default: joined)             
  --raw                  Use to output a raw jar file without any MCPConfig     
                           transformations.                                     
  --sas [File]           Side Annotation Stripper confg file to apply           
  --searge               Use with --raw to output the raw jar file renamed with 
                           SRG names                                            
  --version <String>     MCPConfig artifact version                             

mcp-data Task:
  Option                Description                                              
  ------                -----------                                              
  --artifact <String>   MCPConfig artifact coordinates                           
  --cache <File>        Directory to store data needed for this program (default:
                          cache)                                                 
  --help                Displays this help message and exits                     
  --jdk-cache <File>    Directory to store jdks downloaded from the disoco api   
                          (default: cache\jdks)                                  
  --key <String>        The key for which data file to extract                   
  --mappings            Use to enable using official mappings                    
  --output <File>       File to place output data into                           
  --parchment <String>  Version of parchment mappings to use, snapshots are not  
                          supported                                              
  --version <String>    MCPConfig artifact version                               
Minecraft Maven has finished, took 0:03.877