seeProgress -- flag to monitor the progress of the multithreaded path tracker

For a long path tracking job, one could check the progress of the computation by checking the end of the output file. A multithreaded path tracker no longer writes the solutions to the output file as soon as they are computed. For path tracking jobs that take a very long time, the lack of information on the progress can be annoying. With seeProgess turned on, every thread will write a message to screen for each path tracking job.