Theme Installer: Handle currently installed themes, add search route, let prev/next refresh collections.

props matveb.
see #27055. fixes #27695.

Built from https://develop.svn.wordpress.org/trunk@28025


git-svn-id: http://core.svn.wordpress.org/trunk@27855 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Improve hook docs for the `wp_enqueue_editor` hook, added in 3.9.

See #16284, #27700.

Built from https://develop.svn.wordpress.org/trunk@28026


git-svn-id: http://core.svn.wordpress.org/trunk@27856 1a063a9b-81f0-0310-95a4-ce76da25c4cd
TinyMCE help modal:
- Don't load the old tiny_mce_popup.js.
- Add the shortcut for <code> and the second shortcut for link to the shortcuts listing.
- Update some of the text.
See #27100
Built from https://develop.svn.wordpress.org/trunk@28027


git-svn-id: http://core.svn.wordpress.org/trunk@27857 1a063a9b-81f0-0310-95a4-ce76da25c4cd