Add commands for editing preference files

This adds two commands to the command palette to edit the default and user SublimeLinter preferences.  This saves the user from going 4 menus deep to do the same.
Merge branch 'preferences-commands' of https://github.com/tschaub/SublimeLinter into tschaub-preferences-commands

* 'preferences-commands' of https://github.com/tschaub/SublimeLinter:
  Add commands for editing preference files
Merge branch 'tschaub-preferences-commands' into dev

* tschaub-preferences-commands:
  Add commands for editing preference files
Merge branch 'dev' of https://github.com/SublimeLinter/SublimeLinter into dev

* 'dev' of https://github.com/SublimeLinter/SublimeLinter:
  Support new error reporting format in coffeescript