BUG: Fixed selection issue due to Close Data action

The problem was when the Close Data Action was triggered you could no longer select model entities. The cause was due to the selection manager not being told there was a new client side SMTK model manager (it was \holding onto the now empty old manager)

The fix was to notify the selection manager when the new model manager was created.

Also - changed the slot signature to remove the proxy being passed in since it was never used.