phpdoc
[mms] Add method to allow any code to register tasks to run on logout.
This should be handled internally within the factory rather than remotely
[mms] Add Horde_Vfs driver.
[mms] Horde_Data now stores temporary data using Horde_Vfs to ensure data persists and that it doesn't overload session storage (Request #11335)

Horde_Core_HashTable_PersistentSession has been added to provide a
solution to allow for "persistent" session storage. This means that the
data is guaranteed to exist for the life of the session (but no more).

This fixes the potential of destroying a session by importing too much
data (e.g. in Turba Import screen).
Fix undefined error, and note that this code really needs to be cleaned up
Add code to VFS hashtable driver to allow stream data to be returned

Will allow us to replace current (duplicate) code currently in IMP.