Added more fine grained groups for parser tests

Added more fine grained groups for parser tests

* Group "ParserTests" which allows to run all parser tests in PHPUnit without running other tests
  related to the MediaWiki parser from group "Parser"
* Dynamically generated groups to only run certain parser tests. All of those groups are the parser
  test file names ("." and "_" replaced) prefixed with "ParserTests_". This allows to easily run
  the parser tests of a certain extension separately without using "parserTests.txt".

Change-Id: I03b87820c2968cf16eba2ac39cd8444a0e4dc41a