Simulation Plot now matches Theory

Turns out we were plotting the 'Synbol Error Rate' instead of the 'Bit
Error Rate' - there are 4 bits per symbol so dividing the number of
errors per simulation by 4 before tallying them up given you the right
answer.

Also made some variable name changes etc... important change is on line
32

Time Taken for 500 Simulation Runs:
Regular FOR loop: 79.2 seconds
Parallel PARFOR loop: 87.2 seconds + worker stuff... so much longer