Add status_type as optional param

[SimonAtWattscout]

• Adds the possibilty to give the status_type [39, 41] as optional parameter
• If None is given status_type defaults to STATUS_TYPE.ACCEPTED.value = 39

[SimonAtWattscout]

Tests fail due to:
E: Failed to fetch mirror+file:/etc/apt/apt-mirrors.txt/pool/main/n/nss/libnss3-dev_3.49.1-1ubuntu1.9_amd64.deb 404 Not Found [IP: 52.147.219.192 80]
Fetched 4334 kB in 1s (7749 kB/s)
E: Unable to fetch some archives, maybe run apt-get update or try with --fix-missing?

Looks like mirror config is not up to date

[SimonAtWattscout]

Please hold with the merge, something else has to change first

[SimonAtWattscout]

Okay after a lot of discussion with elhub this finally works. The problem was that in the WSDL existed Acknowledge ElHubService.METERING_VALUES and AcknowlegdePoll in ElHubService.POOL_METERING_VALUES (typo btw, should be POLL).
So to properly send an acknowledgement ElHubService.POOL_METERING_VALUES service is needed. Also then the namespace for this is ns7 instead of ns4

• change ElHubService.METERING_VALUES to ElHubService.POOL_METERING_VALUES in test
• adds POLL to BRS_ID
• changed to namespace in the factory to ns7

The optional status_type is not needed since elhub does not allow anything else than 39.

Hope this all makes sense

[SimonAtWattscout]

@thomasvolte @jgc31416 can you please review this PR?
Python 3.8 test fails due to lint: FAIL code 1 (10.00=setup[7.92]+cmd[0.29,1.80] seconds)
Should not be crucial and I cannot find the issue there.

Thanks