Folders

This PR brings in further integration for OAE in the following aspects:
 - Activities
 - Search
 - Previews
 - REST Docs
 - Extra functionality such as updating, deleting, ..
I'd prefer something like this:

```
var groups = _.filter(principals, function(member) {
  return AuthzUtil.isGroupId(member.id);
});
var groupIds = _.pluck(groups, 'id');
```