Add SignSideMap for easier working with both-side fields

Signed-off-by: Irmo van den Berge <irmo.vandenberge@ziggo.nl>

src/main/java/com/bergerkiller/bukkit/common/block/SignSideMap.java

@@ -0,0 +1,57 @@
+package com.bergerkiller.bukkit.common.block;
+
+import java.util.Arrays;
+import java.util.List;
+
+/**
+ * Stores two values for both sides of a sign. Makes it easier
+ * to track information about both sides of a sign.
+ */
+public class SignSideMap<T> {
+    private T front, back;
+
+    public SignSideMap() {
+    }
+
+    public SignSideMap(T front, T back) {
+        this.front = front;
+        this.back = back;
+    }
+
+    public T front() {
+        return front;
+    }
+
+    public T back() {
+        return back;
+    }
+
+    public T side(SignSide side) {
+        return side == SignSide.BACK ? back : front;
+    }
+
+    public void set(T front, T back) {
+        this.front = front;
+        this.back = back;
+    }
+
+    public void setSide(SignSide side, T value) {
+        if (side == SignSide.BACK) {
+            back = value;
+        } else {
+            front = value;
+        }
+    }
+
+    public void setFront(T front) {
+        this.front = front;
+    }
+
+    public void setBack(T back) {
+        this.back = back;
+    }
+
+    public List<T> both() {
+        return Arrays.asList(front, back);
+    }
+}