Finish up TSWSceneItem configuration

[caitp]

The SceneItem configuration needs to be completed. Currently, it doesn't really do anything useful.

The OBS API is not crystal clear about how to save/load/etc "data" or "properties" objects. It looks like the main obs app does do this for you, and the way it does is not exposed to the API. It's not always obvious which parts of the API are safe to ignore, since the real target is the obs-studio application.

Some nice things to have (that are not on any agenda) would be:

• Typeahead support for Twitch.tv supported games, via API calls when the user types a space or something. This does not look easy to do in the current libobs API, and may require something extra. Basically, when the user types a few characters, we should send a search query to Twitch, and populate a list with the known game titles available. Usability and all of that.
• Obviously, saving/loading these settings is pretty important. The SceneWatcher also needs a quick way to get at this information saved by SceneItem. Infrastructure is in place for this, but hasn't really been made to work just yet.

[caitp]

TypeAhead support isn't really possible in obs-studio at the moment, there's no way to update the Settings dialog controls when it's already open. So for now, it's stuck as it is.