Implement --log CLI argument with rx and tx options

[slook]

Enables additional logging, and takes an optional list of log categories to enable, with filtering by message code number.

--log categories:

• conn: Connections
• db: Database operations
• msg: Includes both r and t
• r: Received network messages
• rx: Received network messages with hexadecimal bytes
• t: Transmitted network messages
• tx: Transmitted network messages with hexadecimal bytes
• x: Includes both rx and tx
• 1 .. 1003: Filter by message code

Based on PR #81 by @jpdillingham and PR #82 by @mathiascode

[mathiascode]

Alright, maybe this could be an option. Just remember that we're sacrificing extensibility, so don't expect me to consider any future requests regarding advanced filtering or categories.

Do we need combined categories like msg and x if we have a flat list? In my opinion they mostly cause confusion, at least in your msg rx example. Why not go with just rx t?

[slook]

we're sacrificing extensibility ... regarding advanced filtering or categories

This is already quite a flexible arrangement, any more advanced filtering than what's done here would require the parameters to be in a very specific order which would make the command line interface too difficult to understand.

Do we need combined categories like msg and x if we have a flat list? ... they mostly cause confusion

Are you suggesting that it would be less confusing if the presence of an x character enabled hexadecimal mode for whichever direction is specified, such that for instance rx would be equivalent to r x for showing only received bytes, and not having x enable both directions unless neither r nor t were specified?

[slook]

I pushed a change to the cli module to callback an array of values instead of a concatenated string. The advantage is native support for shell quoted strings for proper rejection of misplaced or unexpected inputs, and this eliminates the need for any custom splitting to select log_categories.

Details

This constrains an option to take only its correct amount of values (i.e. zero or one, except for options with `defaults`) which makes the argument parser output more helpful syntax exception messages...

$ soulfind --datebass
soulfind: Unknown option '--datebass'

$ soulfind --database
database: Missing value for <path>

$ soulfind --database long stupid name.db log rx
database: Unexpected value 'stupid'

$ soulfind --database "long stupid name.db" log rx
database: Unexpected value 'log'

$ soulfind --database "long stupid name.db" --log rx "long cat" 1 2 34
Available log categories: 'conn' 'db' 'msg' 'r' 'rx' 't' 'tx' 'x' '0..4294967295'
log: Unknown log category 'long cat'

[slook]

@jpdillingham This is the working branch you can use it like ./bin/soulfind --log rx and it's up to date with master. We would appreciate your feedback as to finding the command syntax understandable and the output does what you need?