Translate the Latex doc to Sphinx doc

Don't rely on the docstrings anymor, which aren't sufficient anyway to generate
this kind of documentation.
diff --git a/doc/index.rst b/doc/index.rst
index b9c80cf..8f1d336 100644
--- a/doc/index.rst
+++ b/doc/index.rst
@@ -13,7 +13,7 @@
 Contents:
 
 .. toctree::
-   :maxdepth: 2
+   :maxdepth: 3
 
    introduction
    install