#7 Add Signature Caching to op_acid_db

[Colin G]

Patch for Barnyard 0.2.0 to cache signature IDs
associated with signatures in the database. Signature
IDs in the database are not the same as a signature SID
in the scope of the database. Normally Barnyard must
query the database with every alert to determine the
signature ID -- way more overhead than necessary. This
patch will reduce the total number of database
transactions by roughly 20%.

[Colin G]

barnyard-0.2.0-caching.patch