Add GUI executable to tweak menus

Adds a new executable that allows manual tweaking of menu thresholds and a quick rate calculation.
To run you need a ReducedSample file (the *.proto) ones.

* All the triggers available in the file are shown, and they can be added or removed from the menu with the tick box on the far left.
* Thresholds are changed in the text boxes, hover over the box to get tooltip saying the name of the threshold.
* If the thresholds are correlated then only the primary threshold can be modified and the rest are scaled according to that.
* Click "Calculate rates" to calculate the rates for the triggers and the total rate.  First column for each trigger is the rate and the second is the pure rate.
* Click "Save menu" to save the menu of the currently active triggers and their thresholds.

Fully functional but a lot of the formatting is ugly.  Could do with some work to tidy it up.  Safe to merge since it only adds functionality.