Implement buzzer. Output to pin12.
Adjust code style
Implement beep function
Delete dead code. Modified beep duration. Modified beep macro
Move beep fequency macro to header
Move LCD hardware setting to ui_init(), draw task to ui_task()
Merge branch 'UI' of https://github.com/rtenv-plus-stm32f4/final-project into metronome
Merge branch 'buzzer' of https://github.com/rtenv-plus-stm32f4/final-project into metronome

Conflicts:
	firmware/metronome.c