Request ID Logging (#1087)

* Add RequestID to the RequestScope

* Expose RequestID to auth & request loggers

* Use the RequestID in templated HTML pages

* Allow customizing the RequestID header

* Document new Request ID support

* Add more cases to scope/requestID tests

* Split Get vs Generate RequestID funtionality

* Add {{.RequestID}} to the request logger tests

* Move RequestID management to RequestScope

* Use HTML escape instead of sanitization for Request ID rendering