Breaking changes: UseErrorHandler & UseErrorPage extensions have been renamed

[kichalla]

After some feedback following extensions have been renamed:

1. UseErrorHandler and related overloads have been renamed to UseExceptionHandler to indicate that only un-handled exceptions are handled in this middleware.
2. UseErrorPage and related overloads have been renamed to UseDeveloperExceptionPage to indicate this middleware is supposed to be used during development scenarios.

The above extensions register middleware which also have been renamed. Since its very common to use the above extensions, following renames should not affect you:

1. ErrorHandlerMiddleware -> ExceptionHandlerMiddleware
2. ErrorPageMiddleware -> DeveloperExceptionPageMiddleware

For any questions related to this announcement, please comment over here: aspnet/Diagnostics#178