Final review of Influxdb collector

[lmas]

This should finalise the influxdb collector.

I believe I have written the system and tests in a somewhat competitive or "antagonistic" way (check the test coverage), so please roast me @gabaxh @SimonPergel @Pake-TU.

TODO:

• Add documentation (system README and project issue).
• Pull new data from zigbee (power consumption etc.).

Known bugs:

• The framework doesn't like running unit assets without published services.
• Can't do anything about printed messages from the framework, while running tests.

[lmas]

I'll add the documentation later today when alone. I also feel honored with your trust in my code, all ok from Pake!