Add: Full support for sid-msg v2 format which
enchanced by the following fields: gid,revision,classification,priority
for each entry which allow pre-population of signature metadata by barnyard2.

The feature could still have some bugs but it should be stable enough
for pre-prod environements.

Add: spo_database keyword "disable_signature_reference_table" which
allow a user to tell the output plugin not to populate the sig_ref table
thus speeding up the startup process when there is alot of signature in
use and that the table is not used for any reason.

Bumped: Build to 323