Improve caching of jar file resources

[hcldan]

#196 Introduces the ability to have classpath:// uri's. We end up needing to scan the contents of a jar for all of the resources in order to serve them up.

The ClasspathResourceFactory is recreated every time, and currently rebuilds the map of file resources in the jar.

Either we should refrain from making so many Factories (why are they not singletons?), or we should cache these resources properly.