Closes #39, closes #37, closes #41; Big refactor in engine Engine has been divided in components: - Assets: to deal with files - I18N: to deal with i18n (duh) - SchemaIO: to read pieces of schema from files - Factory: to convert schema to engine objects - SceneViewer: a libgdx actor that  represents a scene - GameController: controls loading games/scenes and variables - And finally, Engine, that correctly builds all previous components and manages a Stage

The editor is not working right now. We need to rethink some things.