Added Sign MaterialData

By: Dinnerbone <dinnerbone@dinnerbone.com>

paper-api/src/main/java/org/bukkit/Material.java

@@ -65,12 +65,12 @@ public enum Material {
     SOIL(60),
     FURNACE(61),
     BURNING_FURNACE(62),
-    SIGN_POST(63),
+    SIGN_POST(63, Sign.class),
     WOODEN_DOOR(64),
     LADDER(65, Ladder.class),
     RAILS(66),
     COBBLESTONE_STAIRS(67),
-    WALL_SIGN(68),
+    WALL_SIGN(68, Sign.class),
     LEVER(69, Lever.class),
     STONE_PLATE(70),
     IRON_DOOR_BLOCK(71),
@@ -162,7 +162,7 @@ public enum Material {
     GRILLED_PORK(320),
     PAINTING(321),
     GOLDEN_APPLE(322),
-    SIGN(323),
+    SIGN(323, Sign.class),
     WOOD_DOOR(324),
     BUCKET(325),
     WATER_BUCKET(326),