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.

Registry_test all test cases now pass for discovery

Ran all test cases again (no hardware), fixed a few issues. ...

Need to still run this up on the hardware to test properly

OpenThings.Message tests now completed

PARAM_NAME key syntax for OpenThings.Message [set] tested ok

OpenThings.Message now tests attribute set and get. ...

Added decorators for @test_0 and @test_1 to turn tests on and off selectively

setattr tests done on OpenThings.Message

Tested all attribute read services in OpenThings.Message

OpenThings.Message test harness keyed paths tested and working

Characterised usage modes of OpenThings.Message better

Refinements to different parameter formats

Clarified test cases for OpenThings.Message()

Started writing unittest harness for new OpenThings.Message abstraction

Moved test harnesses into separate _test.py modules