MongoEngine models, Group listing and applications

Lot of things changed, angular was introduced, user profiles
were moved to MongoEngine, Group models, and group admin mockup
Accepts a user in a group feature.
Adds the group to the LDAP profile of the user.
Fixes import error and adds removing user from group.
Fixes logic in accepting someone to a group.
Fixes group mapping in LDAP, adds remove from group and fix accepting.
Adds applicants length and empty cases
Refactor group owner into a list of admins. Adds is_group_admin decorator.
Fix ab
Fixes some imports
Adds group search filter and refactors webassets bundles.
Adds admin checking in group administration.
Adds group to the current user when saving new group and accepting.
Renames user collection to users.
Shows groups-info only when one is selected.
If a ldap list attribute does not exist, return an empty list.
Checks that the value is not an empty list when adding LDAP attribute.
Adds reload method for User LDAP object.
Group administrator can now make other users administrator.
Adds pinger attribute to Group and pingable_groups to User.