Apidocs3

This continues my clean up of the API docs, so that we can now build the docs with only a few warnings, instead of the hundreds of warnings and tracebacks it used to spew out. Various bits of the output which were broken have been fixed along the way.

I've also given the API docs landing page a facelift, using the Sphinx autosummary extension. Here's what it looked like before:

![api_docs_before](https://f.cloud.github.com/assets/327925/1546370/9dfa2d24-4d84-11e3-80ab-bc3db2885bf5.png)

And here's the new look:

![api_docs_after](https://f.cloud.github.com/assets/327925/1546374/a54a0f4a-4d84-11e3-88be-fa231fa92bc0.png)

The one part that might be controversial is that the autogenerated docs now exclude all of the `inputhook*` modules. We had already excluded the gtk and wx ones, and the imports from the Qt one were a big source of ugly warnings flashing past during the docs build. So I decided it was simplest to leave them all out. The main API in the `inputhook` module (which doesn't load any of the others on import) is still documented.