* [Qt] Performance improvement for the 5 major tab widgets
Address list, History list, utxo list, contacts list, and request list
now all defer their updates if they are off-screen (isVisible() ==
False), to when they are next shown. This drastically improves GUI
responsiveness on large wallets (with many addresses or a large history)
and also increases the speed of initial wallet synch since as the
address history changes, not as much redundant GUI refreshing happens.
* Tweak on_edited method of MyTreeWidget to be more correct
* tweak