Key for checking for duplicates among dependencies.
The unique characteristics of a dependency are:
1. The basic name. No release versions, no sample classes for packages
(though if you specify only the class and not the package, this is different).
2. The type of dependency (module, package, etc.).
Sample things which ought not be duplicated:
1. Sample classes within a package.
2. The same module with different release versions (use ranged releases as needed).
3. Impl & spec comparisons (the impl comparison is stricter anyway).
4. Different versions of the same thing (makes no sense).