LookupGroup is a model to store lookup groups in the local database, it
is basically used to be able to make relations with other models and to
cache the name of the group.

This method returns True if a user belongs to one or more of the groups
passed as an argument, False if not. The list of groups the user
belongs to is retrieved from the lookup service.

The user receiver adds the visibleName value from lookup for this user
to the last_name variable of the object of the class User.
The group receiver assign the title of the group retrieved by lookup to
the name variable of the object of the class Group

Helpers for templates that include javascript code to call an ajax call
to retrieve users or groups based on the text entered by the user

- Added get_institutions(user), that returns all institutions from
Lookup (if a user is given, then the user institutions are returned
first.
- get_institution_name_by_id(institution_id, all_institutions) returns
the institution name given its id, can be used with a cached
all_institutions to reduce the number of calls to the lookup service in
some cases