[mms] Fix regression preventing caching of any internal DB information.

Commit e759e472810c1aeb7c782a683ec7d4153dc29831 broke caching.

get() *must* have "0" as the second argument, or else the cache lifetime
defaults to 1 second.
Fix cacheid for facebook search results
Released Horde_Db-2.1.1
Development mode for Horde_Db-2.1.2
[mms] Potentially save a call to the contacts backend when viewing HTML messages if no image data is present in the message.