Parse error IDs from checkstyle XML
Respect ids in error formatting
Include ids in error message display
Show IDs in error list
Use a custom face for the error id in the error list

Also adapt existing faces
Add support for extracting ids in error patterns
Extract error IDs in error patterns of checkers

Affects: pylint, flake8, chktex, rubocop, phpcs, perlcritic

Note that phpcs uses checkstyle parsing again.  This might revive the
output issues in #78 and #118, but we choose to ignore these from now
on.  It's not our fault that PHP is broken, and we'll not work around it
anymore.

Also, lower gsjlint level to warning, since it doesn't really report
errors.
Parse error ids from eslint via checkstyle
Parse ids from cppcheck XML
Extract error IDs from cppcheck XML

Also consolidate the test cases of cppcheck