Themes screen: fix the position of the search field. Props jesin, fixes #29556.

git-svn-id: https://develop.svn.wordpress.org/trunk@30747 602fd350-edb4-49c9-b593-d223f7449a82
TinyMCE: manually fire `ExecCommand` when aligning images as we do `preventDefault()` on `BeforeExecCommand` for them. Props avryl, fixes #30565.

git-svn-id: https://develop.svn.wordpress.org/trunk@30748 602fd350-edb4-49c9-b593-d223f7449a82
Editor DFW v2: fade out the Screen Options/Help tabs when open. Props avryl, fixes #30593.

git-svn-id: https://develop.svn.wordpress.org/trunk@30749 602fd350-edb4-49c9-b593-d223f7449a82