Simulator files with changes to constants.

In header.h - Changed all constants to match the project spec (tt, tcpu, tq, tdisk, tio - the same for both interactive and parallel processes). Also added constants for tbs, context switch time, memory, and cache expenses. Times are expressed in seconds.

In sim.c, init() - Added a variable to track number of processes in barrier for synchronization and a variable for the amount of available memory.