#21 change button focus for main window

[Daniel MacDonald]

When I'm using Qtractor, I'm hitting the space key very frequently for obvious reasons. Seeing as qtr doesn't show xruns within its interface, I frequently bring qjackctl to the foreground to check for xruns. I have lost count of the number of times I have accidentally killed my JACK session because I have accidentally hit the space bar, intending to start/stop playback under qtr but because qjackctl still had focus JACK gets stopped and qjack quits instead. This is because the Quit button becomes the default in-focus button when JACK is running.

In this situation I'd much rather qjack default to focusing on the transport play button. Not only is that less disruptive when pressed by mistake, its much more likely to be what the user actually wanted to do anyway if pressed by mistake.