Also remove all the locking that somehow blocked the entire Python program.

The attributes cannot be used before they get written to or otherwise
somehow magically updated.  Therefore I added peoprties with default
values that I assign in the init_device method.

The devices that run in this device server connect to OPC-UA servers
that provide crosslet station stats.

And thanks to Leon for pointing out the hidden GPL file.

The Python modules that the device depends on have to be
specified in the file requirements.txt in the same path
of the device.

Still not there because docker-compose appears to do some
things behind closed doors and I cannot figure them out yet.

Numpy is already installed in itango.

THX Marcel.

I cannot - for my life! - figure out how to log something to the logging system.

This makes it actually possible to print a traceback.

This should allow to install 3rd party packages with pip.