Outputs "Press button" on LCD and waits for button press event, in case of event clear LCD and display button number.

Connection details:
LCD:
	PB0 -> LCD_RS
	PB1 -> LCD_RW
	PB2 -> LCD_E
	
	PA0 -> LCD_D4
	PA1 -> LCD_D5
	PA2 -> LCD_D6
	PA3 -> LCD_D7
BUTTONS:
	PD0 -> COL3
	PD1 -> COL2
	PD2 -> COL1
	PD3 -> ROW1
	PD4 -> ROW2
	PD5 -> ROW3
	PD6 -> ROW4

	COL1	COL2	COL3
ROW1	1	2	3
ROW2	4	5	6
ROW3	7	8	9
ROW4	A	B	C