add parallel fast sync support (#238)
* Add parallel require blocks
* Add fast sync block storage and process
* add fetch blocks timeout process
* Fix oops bug
* add timeoutQueue func
* Fix review bug
* Opz code format
* modify parallelFetchHeaders function
* modify select sync peer logic
* Del unused code
* add blocksTasks struct
* Modify block parallel download mode
* Opz code format
* Fix test case error
* opz code format
* Add fast sync peer err handle
* Fix test case err
* Fix review bugs
* Fix review bugs
* Fix review bugs
* Add test file
* Fix review bug
* Fix fetch headers stopHeader lost err
* Fix locate headers bug
* Opz code format
* Fix review bug
- [DH] netsync/peers/peer.go