Group/User based event broadcast

[D3f0]

Current version does not offer any hints about sending an event to a user or a group of users.

ModelEvents are fixed to model classes, not instances.

In order to support such feature, event naming must be defined, currently appname.ModelName are used. This could be generalized to something like event_prefix.GroupName or event_prefix.UserName.

[Brandl]

+1

This would be great to have!