Continued work to clean up the hires screen shot code and move it back towards

Continued work to clean up the hires screen shot code and move it back towards
a working state.  I still see an anomoly when taking a screen shot from inside
a 3d cockpit, but external (chase/tower) views seem to work well.  I also
added a property to control how many screen-res tiles are generated in the
output.  Theoretically, you can now generate unlimited resolution screen shots,
or limited only by your disk space and patience.

Today I successfully generated a 20*1024 x 20*768 (20480x15360) resolution
screen shot.  If you rendered that at 100 dpi it would cover a poster of
about 17 feet by 12.8 feet.

Good luck trying to display something that big or convert it to anything
useful on a typical PC. :-)