Removes the "Atom Publishing Control Namespace" and use a single namespace throughout the APP spec.
There's no need for two namespaces.
Remove section 11.1.
Implies replacing any "pub:" with "app:" in the following subsections and in appendix B.
Implementations already doing pub:control have to be updated to use "app:control" instead.
Section 11 should probably be renamed also...
For the record, this was added by PaceCollectionControl.