* move common forks and parameters to common params
* port specs over to new format
* fix RPC tests
* parity-machine skeleton
* remove block type
* extract out ethereum-specific methods into EthereumMachine
* beginning to integrate Machine into engines. dealing with stale transitions in Ethash
* initial porting to machine
* move block reward back into engine
* abstract block reward logic
* move last hash and DAO HF logic into machine
* begin making engine function parameters generic
* abstract epoch verifier and ethash block reward logic
* instantiate special ethereummachine for ethash in spec
* optional full verification in verify_block_family
* re-instate tx_filter in a way that works for all engines
* fix warnings
* fix most tests, further generalize engine trait
* uncomment nullengine, get ethcore tests compiling
* fix warnings
* update a bunch of specs
* re-enable engine signer, validator set, and transition handler
* migrate basic_authority engine
* move last hashes into executedblock
* port tendermint
* make all ethcore tests pass
* json-tests compilation
* fix RPC tests: change in gas limit for new block changed PoW hash
* fix minor grumbles
* validate chainspecs
* fix broken import
* fix transaction verification for pre-homestead
* remove old lint silencer
* dispatch requests only to peers with higher TD
* dynamic target for sync rounds
* use round pivots instead of frames, fix test
* fix total difficulty calculation for test client
* fix broken reorg algorithm
* fork test, fix ancestor search
* Allow sync reorg up to pruning history size
* Peer difficulty tracking
* Abort downloading block if received with NewBlock
* Set pruning history to 1200
* Renamed history size field
* move block queue to own module, a couple readability changes
* make block queue generic over verifiable data
also fixes heap size calculation
* make block queue into a more generic verification queue
* some module reoganization
* implement header queue
* clean up verification error messages
