Add night view via ambientlight setting on Flat and Surface maps, add

night-and-day setting to generate both night (default) and day
(prefix+'_day') versions of tiles, and add transparency to generated
PNG files

src/main/java/org/dynmap/MapTile.java

@@ -16,6 +16,8 @@ public abstract class MapTile {
 
     public abstract String getFilename();
 
+    public abstract String getDayFilename();
+
     public MapTile(World world, MapType map) {
         this.world = world;
         this.map = map;