Clone mutable regions given to clipboards

Fixes #630

worldedit-core/src/main/java/com/boydti/fawe/object/clipboard/ReadOnlyClipboard.java

@@ -22,7 +22,7 @@ public abstract class ReadOnlyClipboard extends SimpleClipboard {
 
     public ReadOnlyClipboard(Region region) {
         super(region);
-        this.region = region;
+        this.region = region.clone();
     }
 
     public static ReadOnlyClipboard of(final Region region) {

worldedit-core/src/main/java/com/sk89q/worldedit/extent/clipboard/BlockArrayClipboard.java

@@ -63,7 +63,7 @@ public class BlockArrayClipboard implements Clipboard {
 
     public BlockArrayClipboard(Clipboard clipboard, BlockVector3 offset) {
         this.parent = clipboard;
-        Region shifted = clipboard.getRegion();
+        Region shifted = clipboard.getRegion().clone();
         shifted.shift(offset);
         this.region = shifted;
         this.origin = shifted.getMinimumPoint();
@@ -84,7 +84,7 @@ public class BlockArrayClipboard implements Clipboard {
         checkNotNull(parent);
         checkNotNull(region);
         this.parent = parent;
-        this.region = region;
+        this.region = region.clone();
         this.origin = region.getMinimumPoint();
     }