Recursive registries resolution when adding a dependency

As a Nuxeo application developer, when on a given Studio project, I add a dependency in Studio application definition to a package that has itself a dependency toward another package, the registries of the Studio project are updated with the registries information of all sub-packages that are pulled by the dependency.

AC:

• Registries merge is properly covered
• I have access to all my inner dependencies registries
• Registries merge is ordered by package depth; deepest first, then it will move to the next level that has other packages, moving alphanumerically across a level , it will look for the deepest dependency of the next package, and so on
• Registries computation is done during the project loading
• When I remove a dependency from an upstream Nuxeo Package, his corresponding registries are gone.
• Dependency is tested at depth level 6 
• Studio project loading time Overhead of having dependencies should not go beyond 5 seconds