Add bonding functionality to Bluetooth Low Energy BLE

I have just noticed whilst going through some code that the low energy Bluetooth in Qt doesn't support bonding with devices - there is no function to bond with devices and if you try reading from/writing to a characteristic that needs authentication then instead of attempting to bond (like with iOS and android) it gets disconnected with a 'connection reset by peer' message.

It would be good to have either a bond function, an event for if another device attempts to bond (with an option to accept or decline) and an error code if you attempt to read from/write to a characteristic that needs authentication saying that authentication is required.