Implement preliminary Telemetry reporting

[jonathanmayer]

Probably the easiest starting point is to wrap components of the Shield study add-on template in a new utility module. Studies could use the utility module to handle Shield study configuration, eligibility checking, lifecycle management, and Telemetry pings.

A few sources to draw on:

• A prior Shield extension by @biancadanforth et al.: https://github.com/mozilla/price-tracker/
• The Shield study add-on template: https://github.com/mozilla/shield-studies-addon-template/
• The Shield study add-on library: https://github.com/mozilla/shield-studies-addon-utils

For purposes of our early December deadline, let's try to at least have placeholder Telemetry reporting done (i.e., we can queue up some basic aggregate statistics).

[akohlbre]

placeholder code in 3d99b77

[jonathanmayer]

From the December 6 call with Mozilla:

• Telemetry schemas are maintained in a GitHub repo: https://github.com/mozilla-services/mozilla-pipeline-schemas

• The schemas are automatically integrated into the Telemetry pipeline from that repo.
• If there's an issue with a schema, the ping is interpreted in a default string format.
• We're tentatively planning on two layers of ping schemas, both of which would reside on the repo.
  • An outer envelope with a study name and encrypted blob, and possibly other attributes. Not specific to an individual study.
  • An inner set of research data. Specific to individual studies.
• We should look closely at the prior Pioneer schema, which might be reusable: https://github.com/mozilla-services/mozilla-pipeline-schemas/blob/master/schemas/telemetry/pioneer-study/pioneer-study.4.schema.json