Fixed issue: Label for bulk actions shows in common style
Fixed issue: Fixed PHPDoc, cleanup code
Updated translation: Amended russian
Fixed issue: Cleanup comment list view
Fixed issue: Fixed Controller_Admin_Comment

- Added new _prepare_list() method that prepare DataTables list
  for all actions
- Removed all of the same code from all actions. Moved to _prepare_list
- Cleanup code
- Controller code has become shorter twice
Fixed #444: Removed not needed System class