SourceLayout: shuffel UserRequest into Auth:: namespace

SourceLayout: shuffel UserRequest into Auth:: namespace

No logic changes, symbols and debug only.

* shuffle AuthUserRequest to Auth::UserRequest
* shuffle AuthBasicUserRequest to Auth::Basic::UserRequest
* shuffle AuthDigestUserRequest to Auth::Digest::UserRequest
* shuffle AuthNegotiateUserRequest to Auth::Negotiate::UserRequest
* shuffle AuthNTLMUserRequest to Auth::NTLM::UserRequest

* polish and add documentation for several parts of the hierarchy

* replace obsolete debugs() location texts