Add ability to rearrange and edit styles from the Style Manager tab

The style manager tab isn’t especially useful right now, because all it does is let you see what styles exist and rename them. It would be nice to also be able to do the following directly from the style manager:

  1. Open styles for editing
  2. Delete styles
  3. Modify nesting order

If those capabilities were added, the style manager and style system would be more user-friendly in general and especially friendlier to users who are accustomed to manually writing/managing CSS.

I also like the ideas mentioned here, as well as the idea of customizable sort order.