Adding all Entities into CraftBukkit.

These are needed to properly allow for determining class type, in
accordance with current practice.

src/main/java/net/minecraft/server/EntityFallingSand.java

@@ -0,0 +1,78 @@
+package net.minecraft.server;
+
+public class EntityFallingSand extends Entity {
+
+    public int a;
+    public int b;
+
+    public EntityFallingSand(World world) {
+        super(world);
+        b = 0;
+    }
+
+    public EntityFallingSand(World world, double d, double d1, double d2, int i) {
+        super(world);
+        b = 0;
+        a = i;
+        this.i = true;
+        a(0.98F, 0.98F);
+        H = J / 2.0F;
+        a(d, d1, d2);
+        s = 0.0D;
+        t = 0.0D;
+        u = 0.0D;
+        M = false;
+        m = d;
+        n = d1;
+        o = d2;
+    }
+
+    protected void a() {}
+
+    public boolean c_() {
+        return !G;
+    }
+
+    public void b_() {
+        if (a == 0) {
+            q();
+            return;
+        }
+        m = p;
+        n = q;
+        o = r;
+        b++;
+        t -= 0.039999999105930328D;
+        c(s, t, u);
+        s *= 0.98000001907348633D;
+        t *= 0.98000001907348633D;
+        u *= 0.98000001907348633D;
+        int i = MathHelper.b(p);
+        int j = MathHelper.b(q);
+        int k = MathHelper.b(r);
+
+        if (l.a(i, j, k) == a) {
+            l.e(i, j, k, 0);
+        }
+        if (A) {
+            s *= 0.69999998807907104D;
+            u *= 0.69999998807907104D;
+            t *= -0.5D;
+            q();
+            if ((!l.a(a, i, j, k, true) || !l.e(i, j, k, a)) && !l.z) {
+                a(a, 1);
+            }
+        } else if (b > 100 && !l.z) {
+            a(a, 1);
+            q();
+        }
+    }
+
+    protected void a(NBTTagCompound nbttagcompound) {
+        nbttagcompound.a("Tile", (byte) a);
+    }
+
+    protected void b(NBTTagCompound nbttagcompound) {
+        a = nbttagcompound.b("Tile") & 0xff;
+    }
+}