WCF Host and Diagnostics issues

Does not per-say fix the issues in #919 since they have been fixed in another change in earlier commits. However, during investigation two other WCF and Diagnostics issues where identified and fixed

1. The WCF host did never set the `BasePath` of the `Request.Url` property
2. The diagnostics hook was rewriting the url, for diagnostics requests, in the wrong location, causing the helper page to fail loading resources