http.whiteboard: osgi.whiteboard namespace => osgi.implementation
http.whiteboard: osgi.whiteboard namespace => osgi.implementation

CPEG agreed to rename and repurpose the osgi.whiteboard namespace to be
a more general purpose namespace. This change updated the http.whiteboard
spec to refer to the osgi.implementation namespace.

osgi/osgi,osgi/osgi,osgi/osgi,osgi/osgi,osgi/osgi,osgi/osgi,osgi/osgi,osgi/osgi