Log miner fee (#237)

* Get miner fee written in some wallet plugins

* Return txid and fee for geth. possible problem with txid (zero hash on pending transaction)

* bitgo fee return

* Wallet apis fees save in cryptoAtoms

lib/cash-in/cash-in-tx.js

@@ -57,8 +57,9 @@ function postProcess (r, pi) {
   if (!cashInLow.isClearToSend(r.dbTx, r.tx)) return Promise.resolve({})
 
   return pi.sendCoins(r.tx)
-    .then(txHash => ({
-      txHash,
+    .then(txObj => ({
+      txHash: txObj.txid,
+      fee: txObj.fee,
       sendConfirmed: true,
       sendTime: 'now()^',
       sendPending: false,