Add buttons for easy manipulation of basic triggers from the main display

A bit of a hack, you can still see some magic numbers sprinkled, but from my last pull request I know you like to rewrite these things anyway :)

So the idea is that when debugging some hw you want to easily adjust triggers and recapture with as few clicks as possible. Of course the trade off is with screen space. You could potentially have off,high,low trigger buttons for each channel.

With this implementation there is a small display on each channel label that cycles as you click.

We may also want to consider adding transition triggers using more than just the first trigger stage.