newImitationGroup creates an imitation group for testing
 
    An imitation group behaves mostl the same way as a group
    created by HebiLookup, without the requirement to have
    physically connected devices on the network.
 
    The main differences are as follows
 
    * Commands immediately set the corresponding feedback without
      veryfing physical feasibility. Values will be visible in
      the next feedback.
 
    * Imitation devices do not update setting fields (e.g. name)
 
    * There is no feedback for physical sensors such as IMU data
 
    Example:
      % Create an imitation group
      numModules = 1;
      group = HebiUtils.newImitationGroup(numModules);
  
      % Generate log data
      cmd = CommandStruct();
      logFile = group.startLog();
      t0 = group.getNextFeedback().time;
      t = 0;
      while t < 5
          fbk = group.getNextFeedback();
          t = fbk.time - t0;
          cmd.position = sin(2*pi*t);
          group.send(cmd);
      end
      logStruct = group.stopLog();
  
      % Visualize commands
      plot(logStruct.time, logStruct.position);
      hold on;
      plot(logStruct.time, logStruct.positionCmd, ':');