Actions example

[mwcz]

Don't merge yet! Still in progress. Just opening for in-progress discussion.

This PR takes @nwforrer's activate_object example and adds an action system as described in the spec.

Then the scope spread a bit and I also added automatically preloading assets based on the contents of the map json file.

• draft action system and wire up light switch to ceiling light with action chain
• automatically preload assets based on the map.json file
• automatically create objects based on the map.json file (map.createFromObjects())

[Jared-Sprague]

I love it! The only improvement I think would be to include an example of how to run a custom action.

[Jared-Sprague]

reference to #45