RTL for TinyMCE:
- Add _dir: 'rtl' to the TinyMCE translation object.
- Fix editor.css for RTL.
- Fix the Edit and Delete buttons position for wpview and images.
- For _mce_set_direction(), update documentation and fix adding the 'ltr' button.
Fixes #27773

git-svn-id: https://develop.svn.wordpress.org/trunk@28094 602fd350-edb4-49c9-b593-d223f7449a82