Bug 427887: Allow to sort working sets in CNF/Project Explorer

* Replaced Set with arbitrary sorters with List
* Addition of method on WorkingSetManager to control order
* Addition of UI elements on Dialogs to move WS up/down

Signed-off-by: Mickael Istria <mistria@redhat.com>
Change-Id: I0ab1786b4a7ad3943a06b5bea2e58d9a1959d8f5