[#690] Authenticated interaction with Amazon S3

Implements authenticated requests using Amazon S3 REST api

* Backward compatibility:
  * Devices running `1.x.x` APK expect that  `/surveys/*` is public. So survey definition will remain public
  * Devices running `1.x.x` APK will upload data to `/devicezip/*` and marked as `public-read`, when the server gets the notification for data ingestion, the first action is to mark the object as `private`
I remember you mentioning something about selecting a certain expiry period for this.  Perhaps that information could also be included in the email...?