Write more documentation

Sphinx autoapi also now only shows subpackages 1 level deep. This prevents us having a huge long list. Also don't show private or special members. Also show imported members so ifcopenshell.file and ifcopenshell.entity_instance works in docs too.

src/ifcopenshell-python/docs/_autoapi_templates/index.rst

@@ -0,0 +1,16 @@
+Python API Reference
+====================
+
+This page contains auto-generated API reference documentation [#f1]_.
+
+.. toctree::
+   :titlesonly:
+   :maxdepth: 1
+
+   {% for page in pages %}
+   {% if page.top_level_object and page.display %}
+   {{ page.include_path }}
+   {% endif %}
+   {% endfor %}
+
+.. [#f1] Created with `sphinx-autoapi <https://github.com/readthedocs/sphinx-autoapi>`_