Convert Bartik to use inline RTL styles

This is a replacement PR for https://github.com/backdrop/backdrop/pull/300, which included a minor CSS cleanup (it's still the first commit listed here).

Backdrop issue: https://github.com/backdrop/backdrop-issues/issues/207

This version includes a full conversion of Bartik to use inline RTL styles instead of a separate file. We still have a lot of other conversions to include, but the patch at https://drupal.org/node/2015789 is so entirely different from the state of things in Backdrop we may have to rebuild the conversion from scratch.