Let's add a bit of whistles to the admin panel: AJAX removal of themes

Signed-off-by: emanuele <emanuele45@gmail.com>
Possible fix for #645

Signed-off-by: emanuele <emanuele45@gmail.com>
Applied Ant/StealthWombat's suggestions

Signed-off-by: emanuele <emanuele45@gmail.com>
Merge pull request #648 from emanuele45/themes_admin

Themes admin