Square

• Ensuring compatibility with pyvisa v11.1: (issue #2)
  • PYVISAs write() does not return the status code anymore, so the module is modified accordingly
  • not necessary to have an empty query after write_binary_values() in set_custom_waveform()
• Added check_pyvisa_status(), now checking status for both queries and writes
• Bug fixes for set_frequency() and set_offset() that were previously not taking into account the unit when calculating if it was within the limits