Fixed laser control, sped up processing, M652

Fixed laser control, sped up processing, implemented M652 S* for laser
power control, fixed homing sequence so there are no issues once you
home an individual axis other than the Z axis. Before the homing fix, if
you homed the X or Y axis, moved the X or Y axis, and then homed again
it would send the E axis flying toward what it thinks 0 is.