Document api modules and require explicit imports of API submodules

src/ifcopenshell-python/ifcopenshell/api/spatial/__init__.py

@@ -16,7 +16,16 @@
 # You should have received a copy of the GNU Lesser General Public License
 # along with IfcOpenShell.  If not, see <http://www.gnu.org/licenses/>.
 
+"""Assign spatial relationships such as when an element is in a space
+
+Physical elements (walls, doors, etc) may be contained in or reference spatial
+elements (spaces, storeys, buildings, etc).
+"""
+
+from .. import wrap_usecases
 from .assign_container import assign_container
 from .dereference_structure import dereference_structure
 from .reference_structure import reference_structure
 from .unassign_container import unassign_container
+
+wrap_usecases(__path__, __name__)