Initial improvements to RTL language support

Needs much more work, but this is a start

git-svn-id: http://textpattern.googlecode.com/svn/development/4.x@5509 2fea6a4d-a838-0410-917b-93a53c48e9d2
Fix logo alignment in Classic theme RTL

git-svn-id: http://textpattern.googlecode.com/svn/development/4.x@5510 2fea6a4d-a838-0410-917b-93a53c48e9d2