Issue 5436: Admin custom logo feature - Update

TIcket Link: http://atutor.ca/atutor/mantis/view.php?id=5436

I have made couple of changes 
- added labels to "Enable/Disable" radios
- changed the footer template files for all themes and for ATspaces theme made an exception and handled it differently
- admins can enable already existing custom logos without getting any error messages.