added ability to remove markers, and buttons for add/remove marker modes
marker code mostly fixed
code mid-semester demo, multiple markers can be shown at once
rotation now locked, and doesn't crash if GPS isn't locked (asks user to
enable GPS)
added custom map marker class file
added buttons to increment water level, live updating of drawing while 
slider is moved
added some files previously missing from git
replaced bitmap markers with buttons to prevent nasty scaling/resolution
independence problems