Remove TileFeature subclasses.  Add components to TileFeatureObject's when they're added to the scene.
 - Add TilePortalComponent to handle transition features.  I like the name portal more, I think it's more obvious what it does.  thoughts?
 - Add .visible boolean to TileObjects to allow hiding objects in the scene.
 - Remove dynamic class name matching hacks from TileFeatures.  Just use a switch for components... there are only about 10 feature types.
Add skeleton for Ship component.
Add support for syncing components when the host object component list changes.
- Refactor and document ISceneComponent interface to be more explicit.