Add Support for Thermor DG950 Weather Station

[ProfBoc75]

Related to issue #2879

[NicolasGagne]

I have tested this pull request

Here is the actual look

Observation:

• ID: OK 100% match
• Temp: OK 100% match
• Wind Direction: 100% match
• Wind speed: the actual reception unit is on average .1 kph below the given rtl_433 value. (sometime .2 below)
• Rain: Since the transmission unit include only the number of pulse since the last transmission it doesn't give average over the hours but only the average over the last 2 minutes. It seem to transmit the good number of pulse.

Thanks again for you help.

[ProfBoc75]

* Wind speed: the actual reception unit is on average .1 kph below the given rtl_433 value. (sometime .2 below)

Thanks @NicolasGagne for the feedback.

If you agree and acceptable for you, I will merge this PR to rtl_433 master and close the issue.

If you found a better formula, do not hesitate to share, Wind Speed is calculate in lines 164 to 171.

[NicolasGagne]

Sorry I should have said it. It is totally acceptable.

Please merge to master and close the issue.
Thanks