Refactor profiles to always use advanced theme

The current implementation of the tinymce module lets site admins assign different 'levels' of tinymce editing to different roles. Currently the different levels include the three sample 'themes' provided by tinyMCE.

More control over the 'theme' is desirable; both tinyMCE and Drupal lay restrictions on what HTML tags can be used / are passed through, and it would make sense to match these two as close as possible. Out of the three, 'advanced' is the only one that supports customisation of which buttons to show and which plugins to load etc, so this 'theme' would make the most sense to use.

Site admins would - instead of choosing which theme to use - choose which buttons to show for each profile, to match input filters in Drupal. Eventually a drag and drop toolbar editor (per-profile) would be useful.