message: Add transactions per second to getmempoolinfo output
  tps added for transactions accepted into the mempool.
  Tidy up formatting for getmempoolinfo help
diff: @@ -1034,6 +1034,14 @@ UniValue mempoolInfoToJSON()
  size_t maxmempool = GetArg("-maxmempool", DEFAULT_MAX_MEMPOOL_SIZE) * 1000000;
  ret.push_back(Pair("maxmempool", (int64_t)maxmempool));
  ret.push_back(Pair("mempoolminfee", ValueFromAmount(mempool.GetMinFee(maxmempool).GetFeePerK())));
  + try
  + {
  + ret.push_back(Pair("tps", boost::lexical_cast<double>(strprintf("%.2f", mempool.TransactionsPerSecond()))));
  + }
  + catch (boost::bad_lexical_cast &)
  + {
  + ret.push_back(Pair("tps", "N/A"));
  + }
  return ret;
  }
  @@ -1050,6 +1058,7 @@ UniValue getmempoolinfo(const UniValue &params, bool fHelp)
  " \"usage\": xxxxx, (numeric) Total memory usage for the mempool\n"
  " \"maxmempool\": xxxxx, (numeric) Maximum memory usage for the mempool\n"
  " \"mempoolminfee\": xxxxx (numeric) Minimum fee for tx to be accepted\n"
  + " \"tps\": xxxxx (numeric) Transactions per second accepted\n"
  "}\n"
  "\nExamples:\n" +
  HelpExampleCli("getmempoolinfo", "") + HelpExampleRpc("getmempoolinfo", ""));
  