Ensure types used in telemetry are strongly typed

[DonJayamanne]

Ensuring the type names map easily to the telemetry names, makes it easier to discover (avoids having to document or keep documentation in sync) properties captured in the Telemetry.

We should also consider adding strongly typed members for the durations component of telemetry.

[DonJayamanne]

Benefit of the change:

• Today when we use sendTelemetryEvent we pass in the event name and some properties. The two go hand in hand. However there's no way to ensure that we pass in all valid properties for a given telemetry.
  This PR will ensure that given a telemetry event we can define the exact telemetry properties that are expected.
• Benefits - strong typing & looking at one file we can tell exactly what will be captured.

[DonJayamanne]

Fixed in latest release