NEW: Added new Tomcat Maven plugins to parent POM.

CHANGED: Moved some dependencies to dependency management in Parent POM.

CHANGED: Excluded xml-apis dependency from Bagit which cause issues with
org.w3c.dom classes in JDK7.
FIXED: Removed a not null constraint from access_logs.user_fk so
requests from anonymous users can be logged.
NEW: Added Bag Verification functionality.
FIXED: Added back some previously removed dependencies from parent POM.
FIXED: Fixed an NPE thrown when the payload directory did not exist in a
bag.