Snapshots: in-memory snapshots are also restricted to the records defined in...

Snapshots: in-memory snapshots are also restricted to the records defined in the snapshot configuration now

BabuDB: added interface for reverse prefix lookups

git-svn-id: https://babudb.googlecode.com/svn/trunk@134 d4c7dd96-b7b2-11dd-893d-d98698f66bbf