newGroupFromLog replays data from a log file
 
    This method creates a group that retrieves data from a log
    file rather than from the network. This can be very useful
    to test algorithms that need to run on live group data.
 
    The replayed data is deterministic and is suitable for unit
    tests.
 
    Example:
       % Create a log
       group = HebiLookup.newGroupFromFamily('*');
       logFile = group.startLog();
       pause(10);
       logStruct = group.stopLog();
 
       % Replay log until the end
       group = HebiUtils.newGroupFromLog(logFile);
       while true
           fbk = group.getNextFeedback();
           if isempty(fbk)
               % stop at the end of the log
               break;
           end
           display(fbk.position);
       end