Added MIHO033 OpenSensor to Devices.py

Tested and tweaked for Python 3 support

Tested demos on real hardware. Works fine. ...

Observation: handling of incoming messages does not check registry,
it only checks the router, so if you don't have a device object
bound to it, it will be seen as unknown. Needs fixing, but not a high
priority.

Tested setup_tool.py on real hardware - works OK ...

Some tweaks required but now works fine

All test cases now run fine. ...

There is no capture/compare at the moment, so verification is manual

All testers except Registry_test now running all tests

Rationalised all comment styles. ...

The double hash (##) is reserved for commented out lines of code.
The single hash (#) is reserved for normal comments.

Moved setup code from global scope of Registry to energenie.init() ...

This makes it possible to use the registry in test cases

auto variable create example added. ...

Tested in simulation, seems to work, but need to re-test on hardware

Energy monitor example written. ...

Not tested yet, as need to test with real devices

Standalone discovery example written. ...

Not able to test until real devices added

Iterator added to registry

control_mihome.py recoded to use remembered registry

control_legacy.py simplified, assuming learning done by setup_tool.py

setup_tool tested in simulation and works OK

setup_tool now written, ready to start testing

About half of the setup tool is written and roughly working

Receive counter implemented and tested

Devices_test is now a unittest

All registry tests now pass. ...

Requirements list reviewed.
TODO list updated for next steps

Most of Registry_test completed. ...

Just need to write code that passes the 'rx routes created' test

KVS all test cases pass

KVS.DEL() passing tests

Factory creation in ADD is now working

kvs remove functionality working

KVS.remove() test now passes

KVS tested in non persisted mode and works. ...

KVS mostly tested in persisted mode, but more code to write and test

KVS tests for non persistent KVS all pass

Test harness and functionality for KVS defined

Moved KVS to separate module with separate test harness. ...

Will test this in isolation first before integrating with Registry