QT GUI Sink

This is essentially just a combination of the following four GUI's, putting each one in a separate tab.
 * 1) QT GUI Frequency Sink
 * 2) QT GUI Waterfall Sink
 * 3) QT GUI Time Sink
 * 4) QT GUI Constellation Sink

It also provides some extra widgets (e.g. window type) that are usually only accessible either through the block parameters or by middle-clicking the window while it's running.