Ship Glimpse.AI for 2.0.0-beta3 package

[SergeyKanzhelev]

Changes:

1. Use EventSource https://github.com/Microsoft/ApplicationInsights-dotnet/blob/master/src/Core/Managed/Shared/TelemetryClient.cs#L325 instead of TelemetryChannel for the framework 4.6
2. Use ITelemetryProcessor instead of ITelemetryChannel to hijack telemetry items for other versions of Framework
3. Use Cloud context as a name
4. Mark request as either sampled or not depending on samplingRate setting