esc_calib: Changed cmdline interface (now same as for the pwm systecmd), read in the number of channels available, don't make the esc_calib dependant on min/max/disarmed values
pwm_output: Allow PWM values from 900us to 2100us but use a default of 1000us to 2000us
Merge pull request #502 from PX4/pwm_ioctls

more esc_calib enhancements