listing groups must be faster

There are several situations where listing a group is taking too much time for users that have too many groups. For example Joshua or demo user.

At least the following situations:

• add-path: add into my collection
• MyCurriki's "Groups" tab

We should find the individual cases where this happens and fix the individual queries. The general problem seems to be that one monster-gun is used for just about any group-listing purpose. And that one is making several (too many) hibernate queries.