Introduce error messages

Log an error in the test result if the test was not finished. If the
bag file is corrupted or the no status message was received, abort the
analysis
Use ROS_MASTER_URI instead of roslaunch's -p arg

When running various roslaunches on different ports, it's more reliable
to set the ROS_MASTER_URI to http://localhost:port instead of using the
-p argument from the roslaunch command. The latter often causes an ros
/run_id conflict
Remove unnecessary import
Remove unnecessary function
Add an option deleteOnError to delete erroneous bagFiles

You can pass the option deleteOnError to either of the launchfiles
analyse_bag_file and analyse_remaining_bag_files. Valid options include
'ask', 'yes', 'no'.
If you pass ask, the user is prompted to specify if he wants to keep or
delete the bag file. If he passes yes or no to either the argument or
the question the bag file is deleted/kept respecitvely.