Shader refactoring. Fix blending issue with transparency.
Move requestAnimationFrame stuff into preamble section.
Add a couple of new tilesets to play with.
Pull shader apart so we can start generating it procedurally.
More reorganizing.
Remove old shader. Add final shader string to console output.
make the zoom factor (the big pixel size) a uniform
make the atlas size a shader constant
automatically compute the tile size
optimize away useless divisions
move plane-generic stuff out of the "fg-plane" section
make the plane sizes shader constants
make the toc size a shader constant
fix up the plane sizes changes
use generic notation for texture unites (TEXTUREn ---> TEXTURE0 + n)
bind our only vertex attrib to location 0. this can prevent browsers from having to do silly emulation work when running on desktop OpenGL
move fg plane declarations back to fg plane section