CAS-1307: Employ Spring namespaces in overlay context files

This is the second leg of CAS-1307, which adds the needed namespaces (mostly `c`, `util` and `context`) to the context files used for the webapp and the management webapp to be used in the overlays. I skipped over the test resources as they are mostly and primarily used for development internally and aren't part of the maven overlay. 

This changeset has been tested and deployed with success! :)

JIRA: https://issues.jasig.org/browse/CAS-1307