Touchscreen GUI, and some other helpful things

One other comment I'll add is I'm certain I'm doing much of this "wrong" in the sense that I'm overbloating the code with flexibility and functionality. I'm new to the MCU world, so am not particularly sensitive to keeping things compact and to the essentials for a small memory footprint.

I plan to do a bunch of optimization after I get this all working, throwing out stuff that really isn't necessary in this environment. Also, as mentioned above, the plan is to make a basket of individual modules that can be loaded as needed for particular UI elements, so not all the code needs to be taking up space if it isn't used.