Figure out how to deal with game UI

[gajop]

Game UI will almost definitely interfere with if left unchecked.
There are a couple of ways this can be dealt with if we still want to display the game UI:

1. Create custom code for each game that tells it where to put its UI. Most definite to work but very time consuming and requires too much cooperation.
2. Modify or override game Chili to support setting and respecting dimensions for screen0 and its children. This would give us support to enforce game resolution if they use Chili, but require that they either update Chili or that the override of screen.lua and other necessary files is generic enough.
3. Modify engine to lie about actual screen resolutions to the game, but still give us accurate information to SB.

In addition to this, we can also have SB hide the game UI completely when editing, and hide itself while displaying the game UI when developing. This is something that should probably be done anyway so gamedevs can test better.

[gajop]

With this commit: f79c9cb we now hide editor or game UI depending on the mode