PyPi v1.4.0

Major code quality improvements:

• Using qtpy library instead of my own Qt5/6 mechanism
• Improved _NoDevice mechanism
• Removed redundant attach_device()
• Extra check in Worker_jobs if func is actually a callable
• Using singletons Uninitialized_Worker_DAQ/jobs as default attribute
  values instead of using None. This solves pylint warnings on '... is not a
  known attribute of None'.
• Docstring improvement: create_worker_DAQ/jobs() show full info now
• Docstring improvement: Linking against PySide6, instead of PyQt5
• Improved code quality of the pytest

Potential code breaks:

• Removed Python 3.6 support

• The methods of Worker_DAQ and Worker_jobs have been hidden from the
  API and are dundered now. You should not have been calling them anyhow outside
  of this module. Their functionality was and is still available as safer
  methods available at the root level of QDeviceIO(). Specifically::

  Worker_DAQ.pause() --> Worker_DAQ._set_pause_true() , should use pause_DAQ()
  Worker_DAQ.unpause() --> Worker_DAQ._set_pause_false() , should use unpause_DAQ()
  Worker_DAQ.wake_up() --> Worker_DAQ._wake_up() , should use wake_up_DAQ()
  Worker_jobs.send() --> Worker_jobs._send() , should use send()
  Worker_jobs.add_to_queue --> Worker_jobs._add_to_queue() , should use add_to_queue()
  Worker_jobs.process_queue --> Worker_jobs._process_queue() , should use process_queue()