Dependecy Injection of the RACSignal into the Friends tableVC.

This allows the Friend VC to be reusable with usermatchers signal
filtered in different ways.
Add ability to change filter on Friends screen.

Add a container VC which display 1 selected VC out of an array of VCs.
It is used to hold 3 UserMatchersTableVC, 1 for
each possible value of XIGUserFilter, and switch the displayed VC based
on the selected filter in the XIGUserFilterVC.