Attaching groups to resources with datasets

Acceptance test:

Create Group 1, Group 2, Dataset 1, Dataset 2, Resource 1, Resource 2.

Action | Result
-------- | ---------
Add Resource 1 and Group 1 to Dataset 1 | Resource 1 is a part of Group 1
Add Resource 1 and Group 1 to Dataset 2 | Resource 1 is a part of Group 1 and Group 2
Remove Group 1 from Dataset 1 | Resource 1 is a part of Group 2
Add Group 1 and Group 2 and Resource 2 to Dataset 1 | Resource 2 is a member of Group 1 and 2
Remove Group 2 from Dataset 1 | Resource 2 is a member of Group 1
Remove Resource 1 from Dataset 2 | Resource 1 is not a part of any groups