Add support for Firefox OS

*Follow up from https://github.com/phonegap/connect-phonegap/pull/89*

Hi @mwbrooks,

This is a new version of the patch, rebased, made into a single commit and with `query.version` change removed as requested. Started a new PR because that other one was from master.

I started looking into adding zip deploy support for Firefox OS too. To get it working I added the CORS headers middleware here and I also needed to make a fix to our file plugin implementation. Next I need to add fxos support to org.chromium.zip. It may take a while to get all dependencies released and in good shape, but I kept the CORS change here as it's harmless to other platforms. Happy to remove from this PR if needed.

Thanks!