Python module builds on recent version of setuptools

A change in Python setuptools required a change in the build configuration.
The minimum version of setuptools required is 49

Handle relay module removal correctly

Long running processes like the mqtt daemon would on ly enumerate the relays on startup. If a module was removed later, the daemon would try to use it anyway. Adding relay modules would also required a daemon restart.
This version enumerates the modules each time they are used.

Daemon works properly when no hardware

Added EX_UNAVAILABLE to usbrelayd when there is no devices attached and modified the service file to not restart in this case.

Licence tidying

Made licencing consistent to GPLV2+

Implement library versioning

Library versioning per standard practice added.
In future, library bug fixes will have the minor version incremented while API changes will have the major and soname incremented.

Fedora RPM integration .01

Fedora RPM integration

Fedora RPM integration

Fedora RPM Integration

Made suitable for packaging

Tightened up security around the permissions on the relay,
Added an ini file to usbrelayd
Updated the README

MQTT support

Support for MQTT was added with the addition of usbrelayd. The daemon is started by systemd via a service file. The serial is then published to the MQTT broker for operation. Works best with the dcttech relays which allow th eserial to be changed and the current state of the relay can be queried. UCreatefun relays do not have this capability but can still be used.

Support for Ucreatefun.com relays added

Ucreatefun relays now supported.
Debug (-d) and Quiet (-q) flags added.
Now able to use device path from command line.