Revert Java 1.8 changes. Buildable with Java 1.7

There are still active users on Java 1.7, so building with Java 8
was a no-no. This change reverts the recent migration to Java 8,
allowing JDK 1.7 to compile the code.

This means, at least for the time being, no more Lambda expressions
(Boooooooooooooooo!!)

src/main/java/com/loomcom/symon/devices/Device.java

@@ -30,6 +30,7 @@ import com.loomcom.symon.exceptions.MemoryRangeException;
 
 import java.util.HashSet;
 import java.util.Set;
+import java.util.function.Consumer;
 
 /**
  * A memory-mapped IO Device.
@@ -115,7 +116,12 @@ public abstract class Device implements Comparable<Device> {
     }
 
     public void notifyListeners() {
-        deviceChangeListeners.forEach(DeviceChangeListener::deviceStateChanged);
+        deviceChangeListeners.forEach(new Consumer<DeviceChangeListener>() {
+            @Override
+            public void accept(DeviceChangeListener deviceChangeListener) {
+                deviceChangeListener.deviceStateChanged();
+            }
+        });
     }
 
     /**