Add interface for spawning FallingBlocks and correctly spawn a FallingBlock with the spawn(Location, FallingBlock.class) method. Adds BUKKIT-2282

Also add FallingBlock and methods.

Deprecated FallingSand to emphasize FallingBlock.

By: feildmaster <admin@feildmaster.com>

paper-api/src/main/java/org/bukkit/entity/FallingBlock.java

@@ -0,0 +1,43 @@
+package org.bukkit.entity;
+
+import org.bukkit.Material;
+
+/**
+ * Represents a falling block
+ */
+public interface FallingBlock extends Entity {
+    /**
+     * Get the Material of the falling block
+     *
+     * @return Material of the block
+     */
+    Material getMaterial();
+
+    /**
+     * Get the ID of the falling block
+     *
+     * @return ID type of the block
+     */
+    int getBlockId();
+
+    /**
+     * Get the data for the falling block
+     *
+     * @return data of the block
+     */
+    byte getBlockData();
+
+    /**
+     * Get if the falling block will break into an item if it cannot be placed
+     *
+     * @return true if the block will break into an item when obstructed
+     */
+    boolean getDropItem();
+
+    /**
+     * Set if the falling block will break into an item if it cannot be placed
+     *
+     * @param drop true to break into an item when obstructed
+     */
+    void setDropItem(boolean drop);
+}