- added an option (on by default) to prevent a witness from signing two
blocks in a row because this most likely indicates they have been cut
off from the network.
- added an option where a witness will not produce a block if the
witness participation rate is below a configurable threshold (default
to 33%)
- remove circular dependency with fee_schedule
- unitiy build db_* as database.cpp
- move protocol definitions in separate directory
- combined some objects/evaluators
- combined limit/call evaluator/objects into market_evaluator.*
