zip/jar (archive) loader

[cadorn]

Currently the Narwhal loaders are all based on the filesystem. A module must be in the filesystem in one of the search paths. We need to add hooks to allow a loader to provide "virtual" search paths (for lack of a better term), which map module ids to module factories. This will allow things like modules compiled into the binary, zips, jars, etc.

http://groups.google.com/group/narwhaljs/browse_thread/thread/d812af07b3c6d4c6?hl=en