feat: add batch_id to cash_in_txs

feat: bitcoind sendmany request
feat: check if wallet supports transaction batching

lib/plugins/wallet/bitcoind/bitcoind.js

@@ -79,6 +79,22 @@ function sendCoins (account, tx, settings, operatorId, feeMultiplier) {
     })
 }
 
+function sendCoinsBatch (account, txs, cryptoCode) {
+  return checkCryptoCode(cryptoCode)
+    .then(() => {
+      const txAddressAmountPairs = _.map(tx => [tx.address, tx.cryptoAtoms.shift(-unitScale).toFixed(8)], txs)
+      return Promise.all([JSON.stringify(_.fromPairs(txAddressAmountPairs))])
+    })
+    .then(([obj]) => fetch('sendmany', ['', obj]))
+    .then(res => ({
+      txid: res.txid
+    }))
+    .catch(err => {
+      if (err.code === -6) throw new E.InsufficientFundsError()
+      throw err
+    })
+}
+
 function newAddress (account, info, tx, settings, operatorId) {
   return checkCryptoCode(info.cryptoCode)
     .then(() => fetch('getnewaddress'))