Code clean up.

Move the placement of the sprites and the creation of the
spritepos file outside the generation of the PNG files.
Add a generator for plist files usable by Cocos2d-x.
The PList file generation is optional.

PList files are generated only if --plist is given on the
command line.
Version is 1.0.3
Update the man page with the --plist option.
Update the readme with the --plist option.