Remove the disposeFiles params, move it to a chainable method instead.

This also changes the default to no disposeFiles. Somebody convinced me
that it was a little too harsh in practice. I would love to make this
the default, but ambiguous errors are bad.
Canvas flambe_transparent fix.
Have EmitterMold look for textures relative to the .pex file.
OCD formatting.
FMath @:generic optimization.