Fixed too agressive validation in settings  form

refs #5475

Validation on new location information being run even when a new
location wasn't selected.  Moved to form clean instead of widget clean,
since widget doesn't know if it should run validation or not.
AIP store aware of AIP Pointer file

refs #5159

When storing an AIP, storage service now also grabs the pointer file
associated with it and stores it locally, updating it for the new AIP
location. A new Location purpose of STORAGE_SERVICE_INTERNAL created to store
the pointer.xml files.  Packages store where the pointer file is located.

lxml added as a dependency for parsing XML files.