Added a local directory to put ignoreable stuff.

And a few small things (output from rtbMakeSponzaAtrium -> SponzaAtrium, create image.

Plus write out a png image in any case.

Still making it optional, but this seems to go pretty fast.

Routines under the Examples tree that start with “rtbMake” are treated as callable examples in various test programs, so we don’t want helper functions to start with rtbMake, at least if they are under the Examples tree.

And save a png image out in any case.

# Conflicts:
#	.gitignore

Signed-off-by: David Brainard <brainard@psych.upenn.edu>

(1) Catch unique case when no outfield exists because of CamerasRenderer (2) Fix local pbrt executable command (3) Fixed flipped mexximp scale

Example Scenes Plus Performance Stuff.