Add test to show inker rolling journal. to achieve needs to make CDB
size an option, and also alter the manifest sorting so that
find_in_manifest actually works!
An attempt to get a first inker that can build a ledger from a manifest
as well as support simple get and put operations. Basic tests surround
the building of manifests only at this stage - more work required for
get and put.
Add further descriptions of roles following name changes. Attempt to
simplify manifest management in the Penciller by assuming there is only
one Penciller's Clerk active - and so only one piece of work can be
ongoing
