POSIX-style transparent SoftLinks

I find the existing `SoftLink` class to be a bit clunky, in that you have to call the link object in order to dereference it before you can have access the attributes of the node it's pointing to. This is quite different to how softlinks usually behave, e.g. POSIX-style symbolic links which you can read and write to transparently, just as if you were operating on the target file itself. Making softlinks expose the same attributes and methods as the nodes they target removes the need to include extra boilerplate code when passing them to functions that would normally accept arrays, tables etc.

Here's a first attempt to provide this sort of functionality - I'm sure there may be more elegant approaches, and I'd like to hear your feedback.