remove redundant code in cases in start.cpp

Kalpit: You can put as many cases as you like in a row and they'll all
run the code after the last one. No reason to duplicate that code for
now. (I left the game one separate because we'll soon be doing something
different there.)
clean up global variables a bit, remove dead code

Took out some excessively long comments and functions that we're not
using (we can always go back to the lab version to get them if
necessary). Also, the standard button color should be a const.
clean up start.cpp formatting

It would be a good idea to talk about style conventions -- doesn't
matter what as long as they're all the same.
remove more dead code I forgot

(forgot a test compile, this relied on stuff I removed)