Move ancestry bitmap to earlier to accomodate use by loading logic.
Remove extra debug from shabam/bitmap code.
Add missing parameter to 'shabam-contains? in 'shabam-add.
Because our index points to N+1 bit, increment when considering length.
Rewrite 'sha-ancestors and 'sha-successors to handle bogus commits.
Move 'q macro earlier so we can use it for constructing shabam db.
Adding point-filtering style query.

This is known to be wrong but will serve as a basis for our new query.
Add working shabam build/read/write.

The db value now contains two values - :shabam and :pldb. The :shabam
is a bitmapped ancestry lookup for shas. The :pldb value used to be
the db value.