given a resource path so that it can be smart about loading from files versus
streams depending on what works based based on where the resources are coming
from. Also moved FastImageIO into com.threerings.resource to avoid a dependence
on com.threerings.media in resource.
git-svn-id: svn+ssh://src.earth.threerings.net/nenya/trunk@310 ed5b42cb-e716-0410-a449-f6a68f950b19