Document api modules and require explicit imports of API submodules

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

@@ -16,8 +16,18 @@
 # You should have received a copy of the GNU Lesser General Public License
 # along with IfcOpenShell.  If not, see <http://www.gnu.org/licenses/>.
 
+"""Property sets and quantity sets let you store simple key value metadata
+associated with elements
+
+This is the simplest and most common way to store information about an element.
+For example, if a door has a fire rating, it is stored as a property.
+"""
+
+from .. import wrap_usecases
 from .add_pset import add_pset
 from .add_qto import add_qto
 from .edit_pset import edit_pset
 from .edit_qto import edit_qto
 from .remove_pset import remove_pset
+
+wrap_usecases(__path__, __name__)