Added option to synchronise timestamps betweent SmartThings and InfluxDb

[PeteBa]

Firstly, thanks for such a great SmartApp.

Unfortunately, I am seeing some lag between SmartThings creating an event and that event landing in InfluxDb. This can make it difficult to cross-reference between the two systems as the current behaviour is for InfluxDb to timestamp the event based on when it receives it rather than when it was created in SmartThings.

I have added an option (default is off) to use the SmartThings event creation date as the timestamp passed to InfluxDb. This ensures that the two systems have identical reference points.

Let me know if you are willing to take this on-board. I would be happy to make any modifications you think necessary.

Thanks again, Peter