Fix compilation error on java 7

Author: Zhen

driver/src/main/java/org/neo4j/driver/internal/util/Extract.java

@@ -160,6 +160,12 @@ public Property<V> next()
                         Value value = map.value( key );
                         return InternalProperty.of( key, mapFunction.apply( value ) );
                     }
+
+                    @Override
+                    public void remove()
+                    {
+                        keys.remove();
+                    }
                 };
             }
         };

driver/src/main/java/org/neo4j/driver/internal/util/Iterables.java

@@ -73,6 +73,12 @@ public B next()
                     {
                         return f.apply( aIterator.next() );
                     }
+
+                    @Override
+                    public void remove()
+                    {
+                        aIterator.remove();
+                    }
                 };
             }
         };

driver/src/main/java/org/neo4j/driver/internal/value/BooleanValue.java

@@ -48,7 +48,8 @@ public Type type()
     @Override
     public int hashCode()
     {
-        return Boolean.hashCode( asBoolean() );
+        Boolean value = asBoolean() ? Boolean.TRUE : Boolean.FALSE;
+        return value.hashCode();
     }
 
     private static class TrueValue extends BooleanValue {

driver/src/main/java/org/neo4j/driver/internal/value/MapValue.java

@@ -107,7 +107,8 @@ public <T> Iterable<T> values( Function<Value, T> mapFunction )
     @Override
     public Value value( String key )
     {
-        return val.getOrDefault( key, Values.NULL );
+        Value value = val.get( key );
+        return value == null ? Values.NULL: value;
     }
 
     @Override