Centralize "home view" logic

[shunter]

Right now, it seems the best way to reset to the home view programmatically is to simulate a click on the home button. There should be a more direct interface to reset to home, with or without an animation, perhaps on the scene or maybe the camera. The home view location should be configurable as well, for people who don't want North America as the default. Also, morphing the scene to 3D does not reset to the same home view location as the home button (because the position is hardcoded differently in each place).