HDW tests for PI 517 and 753 controllers + fixes:
* GCS comm fixes: - no param queries - case of replies (0X vs 0x) * 753 fixes: - get_voltage() - _get_pos() - get_hw_info()
* GCS comm fixes: - no param queries - case of replies (0X vs 0x) * 753 fixes: - get_voltage() - _get_pos() - get_hw_info()