With the addition of dependency types and with `py-setuptools` set as
type='build' there are more packages that need to have `py-setuptools`
added as a dependency.
This PR adds that dependency for the following packages:
- py-h5py
- py-networkx
- py-pytables
- py-scikit-image
Package repositories now look like this:
top-level-dir/
repo.yaml
packages/
libelf/
package.py
mpich/
package.py
...
This leaves room at the top level for additional metadata, source,
per-repo configs, indexes, etc., and it makes it easy to see that
something is a spack repo (just look for repo.yaml and packages).
