YUI editor 2.7 support patch

The patch below adds support for YUI 2.7 and fixes quite a number of bugs:

1. Support for 2.7.
2. Code button now saves even when pressed.
3. Some code cleanup.
4. Image upload creates the "images" directory if it does not exist. Previously upload would fail without warning if this subdirectory did not exist.
5. The
versus

is no longer experimental, works on FF as well.
6. You can't include <?php tags. So I've added a filter which you can enable. Specify PHP with tags and the filter turns that into <?php.

The patch also contains fixes when YUI's rich text editor appears multiple times on a page, but not enough unfortunately. So buttons like the table and coder button now appear, but things like the paragraph selection still don't work. Will post another patch for these when I've fixed that.

I appreciate comments and obviously improvements.