FR: Mission Simulation/Preview Feature

from http://scp.indiegames.us/mantis/view.php?id=2935

This feature would allow Fredder's to test out the mission they're working on inside of ~~wxFRED~~ FRED or qtFRED, without needing to boot up the full instance of FSO. Four controls would be added, and their operation is similar to those on a vCR.

Play/Pause: Starts, pauses, or resumes the simulation. All editing functions are disabled during simulation, and most are enabled when the simulation is paused.

Rewind: Rewinds the simulation. Depending on memory needs and how the mission history is saved, this will likely be limited to a few minutes of game time.

Reset: Resets the state of the mission to the very beginning of the mission.

Fast Forward: Advances the simulation by playing at a slightly faster rate than normal.

Skip to End: Plays the simulation at the fastest rate without rendering. Use this to quickly test how a mission will end without sitting through the details.