* Simplify jQuery UI slider CSS and bring into line with admin styles.
* Merge styles into wp-admin.css and colors-*.css.
* Scope the CSS with a class so as not to conflict with the color picker, which also utilizes jQuery UI slider. Authors wanting to use built-in styling for sliders should add a class of `.wp-slider` to the container to be intialized.

props karmatosed, helen. see #23497.


git-svn-id: https://core.svn.wordpress.org/trunk@23581 1a063a9b-81f0-0310-95a4-ce76da25c4cd