Separate WebResponse from C#

[9p4]

Related to #20

To simplify the code, separate the HTML in the WebResponse and use a template instead.

[strazto]

Btw, this is supported (in part) by #34 - in #34 I make a mechanism for serving views from file (It has a different API path, from SSOController, though - /SSOViews instead of /SSO )

This does have significant implications, and I'd rather not move the auth client pages to different endpoints, since that'd involve reconfiguring redirect urls etc.

We could just combine the SSOViews controller into the SSO controller, or otherwise embed it

I haven't directly implemented templating - there's mainly just a question of which templating engine to use.

There seems to be plenty of community support for plenty of things. I'd rather steer clear of Razr or whatever the dotnet integrated stuff is, it seems very opinionated and maybe a bit heavyweight.

Some mustache implementation should be fine, maybe Stubble?