IAccessor is being renamed to IInfrastructure. The places we use it in
this repo can actually use an extension method instead and avoid the
cast, so updating to that.
Mostly just a revert of the commit that removed this functionality, with a few changes:
* Perform proper JavaScript encoding in the script part of the database error page Views/BaseView.cs
* Use the builder pattern in the UseXyz extension methods on IApplicationBuilder (per #184). Also applying this to DatabaseErrorPageOptions to keep things consistent.
* Fixing a few tests that were getting the context from DI but putting it in a using block so that it got disposed (rather than letting DI handle disposing).
Rowan Miller
Hao Kung
ajcvickers
Brice Lambson
mikary