+ Adding support for Admin search of plugin items. A previous rewrite made them fail, but I used the opportunity to add a 'plugins' category, so that you can easily see whether a setting was added by a plugin. (Admin)

Signed-off-by: Nao <nao@wedge>
- Removed smiley and avatar path strings. (Admin, ManageSmileys)

! ManageSmileys UK file was needlessly reproducing all strings from the US version. (ManageSmileys.english-uk.php)

Signed-off-by: Nao <nao@wedge>