Leverage asp.net core 2.0 hosting startup to simplify the usage #54
Description
Currently for asp.net core, user need to inject the telemetry initializer manually (and request/dependency tracking module later once this is checked in #51).
We can leverage the hosting startup functionality to avoid such manual work. AI Kubernetes sdk already implemented that in this release https://github.com/Microsoft/ApplicationInsights-Kubernetes/releases/tag/1.0.0-beta5-2