Fix derp with marker types

Author: TBlueF

src/main/java/de/bluecolored/bluemap/api/marker/POIMarker.java

@@ -28,7 +28,7 @@
 
 import de.bluecolored.bluemap.api.BlueMapAPI;
 
-public interface POIMarker {
+public interface POIMarker extends Marker {
 
 	/**
 	 * Getter for the relative address of the icon used to display this {@link POIMarker}

src/main/java/de/bluecolored/bluemap/api/marker/ShapeMarker.java

@@ -26,7 +26,7 @@
 
 import java.awt.Color;
 
-public interface ShapeMarker {
+public interface ShapeMarker extends Marker {
 
 	/**
 	 * Getter for {@link Shape} of this {@link ShapeMarker}.