Support GA measurement protocol as a destination

[vklimontovich]

Some users want to send data to GA instead of DWH

This issue is about research if this feature will work nicely along with our data infrastructure. Here's a link to GA protocol The preliminary design is:

• User configures mapping that maps incoming JSON into one-level JSON:

{
   "tid": 1,
   "sid": 2
   ....
}

The adapted should treat property as measurement protocol parameter, convert JSON to parameter set and send them to GA.

[vklimontovich]

See #130 for GA data schema