Moved LCD_WriteFramebuffer to it's own method in RaspiLCD.

	All draw functions in raspiLCD write only to the buffer.
	The buffer is then flushed to the screen once every iteration
	in Jukeberry.
Added a Main Menu to the program and made Screens Jukeberry aware.

	All screens now hold a pointer to the Jukeberry object they are a part of.
	So they can send signals like switch screen or shutdown back.
	A Main Menu has been added that allows the user to select the desired function
	and quit the Program.