[mms] Add ability to explicitly set hash table key prefix after instantiation.
[mms] Add Horde_HashTable cache driver.

[mms] Horde_Memcache cache driver is now deprecated in favor of the Horde_HashTable driver.
phpdoc
[mms] Added Horde_HashTable driver.

[mms] Horde_Memcache driver is now deprecated in favor of the Horde_HashTable driver.