Merge Google Analytics with airflow master

[dinigo]

This development preexists the one available in the apache/airflow repo operators for Google Analytics. But trying to keep the SSoT principle, can you try to merge this code with the hocks and Operators for google that can be found in the official repo?

I don't want to do a copy-paste of your code since you wouldn't figure as authors anymore. How should I proceed?

If this repo ins no longer maintained I can migrate this to the official apache/airflow issues.

Cheers and thanks for your work!