Problem/Motivation
The BAT (base-admin-theme) file organization we started to do in Drupal 8 was a fantastic idea. See http://drupal.org/node/1089868
It works really well, but its names conflict with the SMACSS categorization we're using in Drupal 8. "base" and "theme" means something else in SMACSS. So we just need to rename them.
The Forum module does not yet follow the guidelines.
Proposed resolution
forum.css into css/forum.skin.css
forum-rtl.css into css/forum.skin-rtl.css
In addition, since our template files are now in a templates sub-directory of a module, we should do the same for the CSS. Note that the toolbar, tour and views modules already do that.
This is part of the CSS standard described at http://drupal.org/node/1887922
Remaining tasks
This issue is blocked by #1924436: Remove separate CSS_AGGREGATE_SYSTEM aggregate file
After this issue's completion, we still have all the other steps outlined at #1921610: [Meta] Architect our CSS.
User interface changes
none
API changes
The forum.module's CSS files will have new names.
By akmalfikri and Gomez_in_the_South