Nix debug logging.
Don't include source in our normal jar files.

I also moved the super-source into the main source tree and exclude it from
normal compilation via excludes rather than sneaking into the main jar files
by treating it as an extra resource.

Games are going to have to add a <classifier>sources</classifier> dependency on
playn-html, playn-core, webgl and gwtbox2d (if they use it), which is
unfortunate (there's no transitivity in the source artifact world), but having
the source in the main jar file was a hack that confused some build systems. It
also confused things like GWT's devmode and superdevmode because it would see
the source in the target/classes directory as well as the src directory and
would get confused if the classpath happened to be in the wrong order.
Pass scale into canvas image so that we work in non-WebGL mode.
Support for HiDPI in canvas renderer.