Allow the owner of the stepper object to cacluate the maximum step
jerk velocity. This is used to ensure there is no communication error
between mcu and host.
Disable checking of jerk velocity for extruder stepper motors.
Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
All users of max_step_velocity and max_step_accel end up multiplying
by step_dist anyway, so it's easier to store max_velocity and
max_accel.
Signed-off-by: Kevin O'Connor <kevin@koconnor.net>