Redesign qtSelectionManager with only one update Selection SLOT
This MR combines the current input selectionManger SLOTs into
one for simplification.
SelectionModifier enum can be used to
specify diffferent selection mode.
SkipList can be used to specify
which outputport to skip. Meanwhile qtSelectionManager would store
entityRefs instead of UUIDs. UUIDs and multiple outputport signals
would be deprecated in the future.