Limit apply blocks

[heifner]

• Interrupt processing of blocks in tight apply block loop.
  • Provides much quicker shutdown during syncing.
  • Allows v1/chain/get_info calls to return quickly during syncing.
• Restores logging every 1000 blocks during replay.

Note this takes a different approach for main than #921 does for release/1.0 because main has the optimization of not posting a handler_id::process_incoming_block if one already exists.

Resolves #284

[ericpassmore]

Note:start
category: System Stability
component: Internal
summary: Limit apply blocks.
Note:end