DB shape change from v29 to add peer info.
New NetworkRepository to handle above.
Peer handshaking with v2 anti-DoS PoW code.
Handshaking refactored into a state-machine-like enum.
Some peer-related API calls added.
Peers exchange pings, heights, peers.
No actual peer sync yet.
Other changes:
Peer version info taken from Maven build properties/resource file.
AnnotationPostProcessor more resilient when fetching PathItems.
Per-repository session debugging flag that can be toggled at will.
HSQLDBRepository.delete() now returns int so callers can detect
whether anything was actually deleted.
Some renaming to settings.
