Support for env files

[haidubogdan]

This pull request proposes support for .env files.
Maybe it has too much features for the daily usage for these kind of files, but I think it's something to be discussed.
As the feedback progresses I can add more unit tests.

Implementations :

• mime provider for .env files
• coloring support

• coloring options for keyword like values (null, true, false ...)
• interpolated env key features like completion and declaration finder
• partial ticket fix Add comment/uncomment options on .properties, .cnf, .env files #6677 covering env files
• hints for duplicate key assignment
• important file node inclusion for .env file for web and php projects

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[lkishalmi]

Looks strange, that Env files display Editor views as Source Env | History, while others are simple:
Source | History

[matthiasblaesing]

In general good idea. The grammar seems to be incomplete. I entered DB_TEST=demo then inserted a newline and inputted D. Then I got on CLI:

     [exec] line 2:1 missing ASSIGN_OPERATOR at '<EOF>'

This looks like debug output.

Entering TEST (notice the trailing space) yields:

    [exec] line 1:4 missing ASSIGN_OPERATOR at '<EOF>'
     [exec] SEVERE: Lexer org.netbeans.modules.languages.env.lexer.EnvLexer@7856b550
     [exec]   returned null token but lexerInput.readLength()=1
     [exec]   lexer-state: -1
     [exec]   tokenStartOffset=4, readOffset=5, lookaheadOffset=6
     [exec]   Chars: " " - these characters need to be tokenized.
     [exec] Fix the lexer to not return null token in this state.
     [exec] java.lang.IllegalStateException: Lexer org.netbeans.modules.languages.env.lexer.EnvLexer@7856b550
     [exec]   returned null token but lexerInput.readLength()=1
     [exec]   lexer-state: -1
     [exec]   tokenStartOffset=4, readOffset=5, lookaheadOffset=6
     [exec]   Chars: " " - these characters need to be tokenized.
     [exec] Fix the lexer to not return null token in this state.
     [exec] 	at org.netbeans.lib.lexer.LexerInputOperation.checkLexerInputFinished(LexerInputOperation.java:435)
     [exec] 	at org.netbeans.lib.lexer.LexerInputOperation.nextToken(LexerInputOperation.java:193)
     [exec] 	at org.netbeans.lib.lexer.BatchTokenList.tokenOrEmbeddingImpl(BatchTokenList.java:171)
     [exec] 	at org.netbeans.lib.lexer.BatchTokenList.tokenOrEmbedding(BatchTokenList.java:166)
     [exec] 	at org.netbeans.lib.lexer.LexerUtilsConstants.tokenIndexLazyTokenCreation(LexerUtilsConstants.java:307)
     [exec] 	at org.netbeans.lib.lexer.BatchTokenList.tokenIndex(BatchTokenList.java:161)
     [exec] 	at org.netbeans.api.lexer.TokenSequence.move(TokenSequence.java:650)
     [exec] 	at org.netbeans.modules.languages.env.EnvOccurencesFinder.computeOccurrences(EnvOccurencesFinder.java:99)
     [exec] 	at org.netbeans.modules.languages.env.EnvOccurencesFinder.run(EnvOccurencesFinder.java:60)
     [exec] 	at org.netbeans.modules.languages.env.EnvOccurencesFinder.run(EnvOccurencesFinder.java:35)
     [exec] [catch] at org.netbeans.modules.csl.editor.semantic.MarkOccurrencesHighlighter.processImpl(MarkOccurrencesHighlighter.java:157)
     [exec] 	at org.netbeans.modules.csl.editor.semantic.MarkOccurrencesHighlighter.run(MarkOccurrencesHighlighter.java:114)
     [exec] 	at org.netbeans.modules.csl.editor.semantic.MarkOccurrencesHighlighter.run(MarkOccurrencesHighlighter.java:59)
     [exec] 	at org.netbeans.modules.parsing.impl.TaskProcessor.callParserResultTask(TaskProcessor.java:561)
     [exec] 	at org.netbeans.modules.parsing.impl.TaskProcessor$RequestPerformer.run(TaskProcessor.java:786)
     [exec] 	at org.openide.util.lookup.Lookups.executeWith(Lookups.java:288)
     [exec] 	at org.netbeans.modules.parsing.impl.TaskProcessor$RequestPerformer.execute(TaskProcessor.java:702)
     [exec] 	at org.netbeans.modules.parsing.impl.TaskProcessor$CompilationJob.run(TaskProcessor.java:663)
     [exec] 	at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:539)
     [exec] 	at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
     [exec] 	at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:1403)
     [exec] 	at org.netbeans.modules.openide.util.GlobalLookup.execute(GlobalLookup.java:45)
     [exec] 	at org.openide.util.lookup.Lookups.executeWith(Lookups.java:287)
     [exec] 	at org.openide.util.RequestProcessor$Processor.run(RequestProcessor.java:2018)
     [exec] line 1:5 missing ASSIGN_OPERATOR at '<EOF>'

The hint integration shows an untranslated label (first linne in tree):

[matthiasblaesing]

Why is this needed?