Add missing robot types to string conversion

Author: urfeex

include/ur_client_library/ur/datatypes.h

@@ -249,12 +249,16 @@ inline std::string robotTypeString(const RobotType& type)
       return "UR3";
     case RobotType::UR5:
       return "UR5";
+    case urcl::RobotType::UR8LONG:
+      return "UR8_LONG";
     case RobotType::UR10:
       return "UR10";
     case RobotType::UR15:
       return "UR15";
     case RobotType::UR16:
       return "UR16";
+    case urcl::RobotType::UR18:
+      return "UR18";
     case RobotType::UR20:
       return "UR20";
     case RobotType::UR30: