Get Rid of nobuild, nolink, and alldeps (#2765)

* Removing the nobuild, nolink, and alldeps dependency types in favor of being explicit.
* This will help with maintenance going forward, as adding more dependency types won't affect existing declared dependencies in weird ways.
* default deptype is still `('build', 'link')`

var/spack/repos/builtin/packages/python/package.py

@@ -347,7 +347,8 @@ def setup_dependent_environment(self, spack_env, run_env, extension_spec):
         spack_env.set('PYTHONHOME', prefix.strip('\n'))
 
         python_paths = []
-        for d in extension_spec.traverse(deptype=nolink, deptype_query='run'):
+        for d in extension_spec.traverse(
+                deptype=('build', 'run'), deptype_query='run'):
             if d.package.extends(self.spec):
                 python_paths.append(join_path(d.prefix,
                                               self.site_packages_dir))