Install to package dependent subfolder

[per-samuelsson]

Today, doing goodget packages nunit will result in

packages/
  nunit/
    lib/

We are changing this to isolate the grabbed package and bundle it along with all its depedencies (somewhat related to #6), i.e producing instead

packages/
  nunit/
    nunit/
      lib/
    dependency1/
      tools/
    dependency2/
      content