Document api modules and require explicit imports of API submodules

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

@@ -16,7 +16,20 @@
 # You should have received a copy of the GNU Lesser General Public License
 # along with IfcOpenShell.  If not, see <http://www.gnu.org/licenses/>.
 
+"""Create an IFC project
+
+All IFCs must have one, and only one IFC project before any data may be
+associated. If you are starting from scratch, see :func:create_file.
+
+Once a project exists, you may optionally create project libraries and
+associate type assets with it. You may also append assets from other projects
+into your project.
+"""
+
+from .. import wrap_usecases
 from .append_asset import append_asset
 from .assign_declaration import assign_declaration
 from .create_file import create_file
 from .unassign_declaration import unassign_declaration
+
+wrap_usecases(__path__, __name__)