Various updates.

Add segregated witness and regtest, fixes.

Add bip68/112/113 and network.invalid_services.

Eliminate block polling, no announce if stale chain.

Changes in support of backlog fix, optimize config.

Major new features and improved quality.

Required by server v2.4.0.

Required by server v2.1.0.

Required by server v2.2.0.

Required by server v2.0.0.