Implement eth_sendTransaction (#104)

* Set up framework for sending transaction with correct args and nonce mutex locking

* Set up printing ethereum address through emintkeys and getting chainid from flags

* Implemented defaults for eth_sendTransaction

* Fix bug with no data provided

* Updated comments and error, as well as RLP encoded tx bytes for return instead of amino encoded

rpc/args/send_tx.go

@@ -0,0 +1,22 @@
+package args
+
+import (
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/common/hexutil"
+)
+
+// SendTxArgs represents the arguments to sumbit a new transaction into the transaction pool.
+// Duplicate struct definition since geth struct is in internal package
+// Ref: https://github.com/ethereum/go-ethereum/blob/release/1.9/internal/ethapi/api.go#L1346
+type SendTxArgs struct {
+	From     common.Address  `json:"from"`
+	To       *common.Address `json:"to"`
+	Gas      *hexutil.Uint64 `json:"gas"`
+	GasPrice *hexutil.Big    `json:"gasPrice"`
+	Value    *hexutil.Big    `json:"value"`
+	Nonce    *hexutil.Uint64 `json:"nonce"`
+	// We accept "data" and "input" for backwards-compatibility reasons. "input" is the
+	// newer name and should be preferred by clients.
+	Data  *hexutil.Bytes `json:"data"`
+	Input *hexutil.Bytes `json:"input"`
+}