Add method for inspecting module dependency relations

This patch adds mw.inspect#getDependencyGraph, which returns an object
enumerating all the modules that a given module requires and all the modules
that require the given module. There is no special console report associated
with this method.

Change-Id: Ib234c2c8bbbf8f34860b04e8d299b6923f4775ef
Merge "Add method for inspecting module dependency relations"