adjust format for golint (#419)

adjust format for golint  (#419)

* standard transaction reserve utxo filter out contract utxo

* distinguish StandardUTXO and ContractUTXO
modfiy spendUTXOAction into no account, the contract utxo is not need to sign
wallet add contract utxo db
adjust function parameter format: the end of parameter is error

* delete ExtContractTag because contract utxo is stored in ContractUTXO

* spendUTXOAction add situation when account is empty
prevoutDBKeys delete return value
filterAccountTxs filter contract transaction to reduce unrelated transaction

* fix golint for blockchain/account/reserve.go

* optimise the import

* adjust format for golint

* adjust format