Intellisense in VS Code (both jedi and ms python language server) picks
up all imported names and suggests them with equal priority for
code completion. By adding a leading underscore, intellisense lists
these with a lower priority, so they don't get in the way.
Also rename from builtins to _common while we are touching this to
better reflect the intention of the module (it contains types shared
by multiple modules, not builtin types like int).
The documentation currently has a mix of with and without the `s`.
Adding an `s` is consistent with most API documentation in general,
especially more modern documentation.
These are not used by classes in the docs, but they are used by Sphinx.
Also, this will be used to let autocomplete know that these modules contain a Motor class.
Laurens Valk
David Lechner