message: [RPC] Add 'IsValidReason' to 'mnbudget getinfo' output
diff: @@ -446,6 +446,7 @@ Value mnbudget(const Array& params, bool fHelp)
  std::string strError = "";
  obj.push_back(Pair("IsValid", pbudgetProposal->IsValid(strError)));
  + obj.push_back(Pair("IsValidReason", strError.c_str()));
  obj.push_back(Pair("fValid", pbudgetProposal->fValid));
  return obj;
  