Added @return javadoc clause to DBSession.createDBObject() methods
Comment reformat in GanymedeSession.setDefaultOwner javadoc
Make DBSession.createDBObject() take a List<Invid> rather than Vector<Invid>
Made DBPermissionManager use List instead of Vector when possible

Made the newObjectOwnerInvids and the visibilityFilterInvids Lists
unmodifiable for hygiene.
Made GanymedeSession work with the new List-ified DBPermissionManager
Tweaked javadoc for DBPermissionManager.getAvailablePersonae()