Minor renaming and a static abort flag flag added to the QuadPatchJob
Removed ability to cancel terrain jobs.
Added a class static flag to abort all patch jobs.
Added base class for patch jobs, derived single and quad patch jobs.
Changed ALL terrain height and colour to be const to make calling them cleaner.
Made Pi::pJobs into a ScopedPtr so it get's cleaned up at program exit, no longer delete it when leaving a game.