Design of persistent registry store improved after a re-think

monitor_mihome now works with auto join and switch toggling

Factory method added to MiHomeDevice to generate a join_req for testing

Registry_test all test cases now pass for discovery

Set up test case for the final discovery test. ...

Test not run yet, and code is missing, marked with ####HERE####

Join_ack working on discovery mode autojoin

Most test cases for discovery modes implemented and passing

Improved debug output for testing

Refactored usages of raw message to use Message() ...

Removed all usages of showMessage, alterMessage

Marked with ##HERE markers the refactoring required for new Message() ...

Disabled alterMessage showMessage and createMessage to force this issue

Improved separation of test harness messages

Moved test harnesses into separate _test.py modules