Added PLN Manager (LOCKSS) stubs

refs #5425

Added a Space class for the PLN Manager/LOCKSS.  Functionality relating to
the PLN manager on the changes to the METS file are stubs, since those
requirements not yet decided on.

Updated store AIP and download file functions to work with LOCKSS, and
added a stub callback function for when LOCKSS is done storing the file.
Added a new status for a package for when it is on the Storage Server, but
not yet in LOCKSS.
Rename PLN manager to LOCKSS-o-matic