v0.3.31

Fixed

• Ellipsoid.getPositionElevation not returning negative elevations.
• EnvironmentControls: Enfoce a minimum elevation when computing horizon distance to ensure a reasonable far clip distance.
• EnvironmentControls: Contructor arguments are no longer required.
• EnvironmentControls: Detach now correctly removes the dom element reference.
• GlobeControls: Functions without setting indices.

Added

• EnvironmentControls: Add "fallbackPlane" and "useFallbackPlane" members so dragging works when there is no geometry under the mouse.