Provide url inspection/manipulation API via SetUrlManager

[mgravell]

Re-submission of previous API change, but with much cleaner implementation, and without writing in the code-gen'd files. The intent here is to provide an API that we can use to re-route stacman traffic to a different domain to avoid network traversals - but provided in a way that allows general purpose url inspection.

[emmettnicholas]

Looks good, but would there be any reason for someone to need this, outside of internal SE use cases?

Also, I spoke briefly with Craver about having SE take over this repo (+ nuget) package. Maybe we should move ahead with that, rather than relying on pull reqs

[mgravell]

Genuinely, I don't know if anyone else would need it, except perhaps for logging purposes. More than happy to drag the project into the SE name - that's all up to you, though. We have a StackExchange github account (I wonder if we should create a StackExchange nuget account too)

[mgravell]

Note update re user-agent