Merge pull request #1 from maticnetwork/span-sync

cmd/puppeth/wizard_genesis.go

cmd/utils/flags.go

consensus/bor/api.go

consensus/bor/bor.go

consensus/bor/clerk.go

consensus/bor/rest.go

consensus/bor/snapshot.go

consensus/bor/span.go

consensus/bor/validator.go

contracts/validatorset/contract/ValidatorSet.abi

contracts/validatorset/contract/ValidatorSet.bin

contracts/validatorset/contract/ValidatorSet.sol

contracts/validatorset/validatorset.go

eth/backend.go

params/config.go