Parallel Programming - Tidied things up

Since most of the single thread code can be reused, I put in symbolic links for the mthread version.
I added comments. The programs can be run without graphics. They can also output performance info.

Also wrote python script to get performance information and plot it.
I was going to do the OpenMP version, but got carried away with all the "tidying", so I haven't yet.

Curses.