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).
This is not just an alias for a LUMPDevice because it works differently. On ev3dev, sensor modes are set using strings.
Also, simplify the introductory text and reasons for using it.
Laurens Valk
David Lechner