[Fluxus] nuke button + png saving commits

[Dave Griffiths]

> excellent. thanks.
>
> it would be nice if (framedump) worked with the png format also.
> probably it's not a big work now as you have implemented png saving.

no, it's not a biggy - but we should probably tidy it up, as the texture
loading and saving code is separate from the framedump formats (PNGLoader
vs Utils). we should just abstract out an image loader/saver which just
looks at the extension - then get jpg/tiff/ppm loading working to support
them as  texture formats.

cheers,

dave