Add interface to allow bus elements to provide their location.

Allows controller to centrally track chunk load/unload for scheduling scans.

src/main/java/li/cil/oc2/api/bus/BlockDeviceBusElement.java

@@ -0,0 +1,21 @@
+package li.cil.oc2.api.bus;
+
+import net.minecraft.util.math.BlockPos;
+
+/**
+ * Implementing this interface allows providing positional information to the {@link DeviceBusController}.
+ * <p>
+ * Controllers may use this information to automatically trigger bus scans when the chunk containing
+ * this element or a chunk adjacent to it gets unloaded / loaded. This convenience allows not having
+ * to implement logic in bus element implementations to trigger such scans themselves.
+ */
+public interface BlockDeviceBusElement extends DeviceBusElement {
+    // TODO Do we want to support multi-dimensional buses? (have a getWorld)
+
+    /**
+     * The position of this bus element.
+     *
+     * @return the position of this bus element.
+     */
+    BlockPos getPosition();
+}

src/main/java/li/cil/oc2/common/bus/TileEntityDeviceBusElement.java

@@ -1,5 +1,6 @@
 package li.cil.oc2.common.bus;
 
+import li.cil.oc2.api.bus.BlockDeviceBusElement;
 import li.cil.oc2.api.bus.DeviceBus;
 import li.cil.oc2.api.bus.DeviceBusElement;
 import li.cil.oc2.common.bus.device.BlockDeviceInfo;
@@ -22,7 +23,7 @@ import java.util.Optional;
 
 import static java.util.Objects.requireNonNull;
 
-public class TileEntityDeviceBusElement extends AbstractGroupingBlockDeviceBusElement {
+public class TileEntityDeviceBusElement extends AbstractGroupingBlockDeviceBusElement implements BlockDeviceBusElement {
     private static final int NEIGHBOR_COUNT = 6;
     final Direction[] NEIGHBOR_DIRECTIONS = Direction.values();
 
@@ -39,6 +40,11 @@ public class TileEntityDeviceBusElement extends AbstractGroupingBlockDeviceBusEl
 
     ///////////////////////////////////////////////////////////////////
 
+    @Override
+    public BlockPos getPosition() {
+        return tileEntity.getPos();
+    }
+
     @Override
     public Optional<Collection<LazyOptional<DeviceBusElement>>> getNeighbors() {
         final World world = tileEntity.getWorld();