Classpath and class loaders

[andreabergia]

Need to support a concept of "classpath" in the vm.

Also, class loaders should be a hierarchy - not sure if this should be done at the same time as the classpath or not.

[andreabergia]

Partially implemented - the class loader does not really exist, but we have classpath and dynamic resolution of classes at the moment.

[andreabergia]

Won't fix this.