use autosummary to generate most of the API Reference

- custom _template/autosummary/module.rst to include docs
  for all module :members" (shows up directly after the summary
  tables)
- module docs should *not* contain autodocs for members, only general
  descriptions and examples
- all files inside api/ are autogenerated whenever sphinx is run
  (no need to add to the repository, hence excluded in .gitignore)

.gitignore

@@ -4,4 +4,11 @@
 # PIP stuff
 *.egg-info
 # Visual studio code
-.vscode
+.vscode
+
+# editor files
+*~
+
+# generated files
+docs/build
+docs/source/api/*.rst