AnalogMonitor - uses Video Game Shield to plot analog input

The included demo program tv_data_collection looked like exactly what I was hoping to do with the Video Game Shield, but as you may know, the original just plots out a simple equation. My version adds the functionality of plotting data from the analog pins, and allows you to cycle through the inputs by pressing a button (connected to digital in 2 by default). This is a great way to test your inputs and ranges, and visualize things without needing a computer. It's been very useful for testing potentiometers and piezo elements.

In the process, I ended up restructuring the whole thing, removing some individual functions and placing them in the main loop... mainly to format it in a way that I understand more easily, being a programming novice. I also removed several of the places that added frame delays or cleared the screen, which reduced flicker. If I remove the final remaining TV_clear.screen(), the flicker goes away completely, but pixels will stay white once drawn. I'm sure this can be easily fixed, just haven't looked into it yet.