<NME> OverlayImpl.java
<BEF> package cgeo.geocaching.maps.interfaces;

/**
 * Marker interface of the provider-specific
 * Overlay implementations
 */
public interface OverlayImpl {

    public enum OverlayType {
        PositionOverlay,
        ScaleOverlay
    }

    void lock();

    void unlock();

    MapViewImpl getMapViewImpl();
}

<MSG> refactoring: reduce mapsforge memory usage

This puts scale and position into one overlay, instead of using 2
overlays. That reduces memory usage by 2 times a full screen bitmap due
to double buffering in mapsforge.

The only downside is that scale and position now have to be drawn at the
same depth-level (below or on top of the caches), but they were both on
top previously anyway.
<DFF> @@ -6,11 +6,6 @@ package cgeo.geocaching.maps.interfaces;
  */
 public interface OverlayImpl {
 
-    public enum OverlayType {
-        PositionOverlay,
-        ScaleOverlay
-    }
-
     void lock();
 
     void unlock();

refactoring: reduce mapsforge memory usage