Update jQuery UI to 1.11.1.

Because jQUI's build process no longer provides individual minified files we need some additional changes:
* Rename all files, remove the "jquery.ui." prefix. Add old files to `$_old_files`.
* Add and use non-minified files in /src.
* Add grunt task to minify jQuery UI files.
* (Non-minified files will not be shipped.)

Changelogs:
* http://jqueryui.com/changelog/1.11.0/
* http://jqueryui.com/changelog/1.11.1/

props Fab1en, ocean90.
fixes #29833.

git-svn-id: https://develop.svn.wordpress.org/trunk@29847 602fd350-edb4-49c9-b593-d223f7449a82