bugfix(errors): 404 and 405 errors were missing keyword args

Per RFC 7231 6.5 4xx errors should include a message to the user; however
the current code did not allow developers to specify the description, title, etc
for the 404 and 405 errors; all other errors had the keyword args present and
therefore usable. This brings 404 and 405 errors into compliance with the RFC
bugfix(errors): re-enable body on the messages

Change the 404 and 405 errors to allow an optional representation.
Developers should be able to decide whether or not to send the error
message body.  OptionalRepresentation by default behaves like NoRepresentation.
If all were switched, then NoRepresentation should be left for devs to use
in their own error derived classes to force it one way all the time.

No breaking changes