Make app controller prefix handling more dynamic
Add a admin prefix and all the belonging code

This allows the creation of a admin interface for the Mauris
administrators. This way the manage interface can be used for
school/department specific things. Splitting this increases the
security and usability a bit.
Move some user and organization actions to admin interface

Some of the things related to users and creating organizations belongs
to the admin interface not to the manage interface.

This change moves these things to the admin interface.