Add SCARAcal to Smoothieware

Required to ease Angle and Step/angle calibration in SCARA systems
I think this should be replaced with 
               Gcode gc(cmd, &(StreamOutput::NullStream));
                THEKERNEL->robot->on_gcode_received(&gc); // send to robot directly

This reduces the chances of recursion, and is faster. Zprobe does this because it may be a multi gcode command, but in this case it is not. Using on_console_line_recieved here is a waste of time and resources.