Add an FX_When argument to all *set_effect functions. FX_When can either be start, middle, end, or single

Conflicts:
	audio/audio_instrument.c
	common/nsmtracker.h
	common/patch.c
	common/patch_proc.h
	midi/midi_fx.c
Make sure FX are scheduled with highest priority (i.e. ensure effects are sent out before note on), plus clean up the scheduler priority system

Conflicts:
	common/PEQpitches.c