@zelig When blocks are in the future they'll be cached and processed at
a later time. Because of this the returned TD will be much lower than
the broadcasted TD.
- fix status chain map uses common.Hash as key
- add badPeers increment to IncorrectTD errors (forgotten)
- signal head info update to head section process even if parent hash is not in pool (inserted), so that idle timer can be set to nil
- suicideC -> peer.headInfoTimer
- quit -> peer.bestIdleTimer
- and they are properly set from within getBlockHashes and handleSection
- update blockpool td by subscribing to ChainHeadEvent
- if ahead of best peer, demote it
- addPeer now take own td as current td
- removePeer now take own td as current td
- add relevant tests to peers_test
- eth: backend now calls blockpool with eth.eventMux and chainManager.Td
- blockpool moves to its own package
- uses errs pkg for its own coded errors
- publicly settable config of params (time intervals and batchsizes)
- test helpers in subpackage
- optional TD in blocks used now to update peers chain info
- major improvement in algorithm
- fix fragility and sync/parallelisation bugs
- implement status for reporting on sync status (peers/hashes/blocks etc)
- several tests added and further corner cases covered
