Color scheme support for the new theme installer UI.

props ryelle.
fixes #27522.


git-svn-id: https://develop.svn.wordpress.org/trunk@27784 602fd350-edb4-49c9-b593-d223f7449a82
There is no more `video-playlist` shortcode. To use video, it is now `[playlist type="video" ....]`. Also deleting core playlist styles. The `style` attribute is still supported, defaulting to `light`. Our core style support was 4-5 CSS rules. 

See #27552. Leaving open for comments and potential bugs.



git-svn-id: https://develop.svn.wordpress.org/trunk@27785 602fd350-edb4-49c9-b593-d223f7449a82