Add ID field to flycheck-error struct
Fix tag construction in checker test definition
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 rule names as IDs from phpmd
Copy error ids at point

Make flycheck-copy-messages-as-kill obsolete, and add new
flycheck-copy-errors-as-kill, which can copy messages, error ids or both
together.
Update changelog

[ci skip]
[Fix #529] Merge branch 'error-ids'

* error-ids:
  Update changelog
  Copy error ids at point
  Extract rule names as IDs from phpmd
  Parse ids from cppcheck XML
  Parse error ids from eslint via checkstyle
  Extract error IDs in error patterns of checkers
  Add support for extracting ids in error patterns
  Use a custom face for the error id in the error list
  Show IDs in error list
  Include ids in error message display
  Respect ids in error formatting
  Parse error IDs from checkstyle XML
  Fix tag construction in checker test definition
  Add ID field to flycheck-error struct

Conflicts:
	CHANGES.rst
	flycheck.el