Sanitized filename display on RaspiLCD.

	Displayed filenames now look nicer. Only the file name without
	the path is displayed and only the first 21 characters are displayed
	so the display is not overflown.
Added Button support to RaspiLCD.

	RaspiLCD now as an update() function that updates the state of the
	RaspiLCD module... right now only the button states are read
	and saved in member variables.