Restructure PaperSpigot as a new set of modules

Allows us much greater control over the Spigot portion of the code
and makes us more "proper"
Credit to @Dmck2b for originally passing the idea along a while back

CraftBukkit-Patches/0135-Check-Skull-canPlace.patch

@@ -0,0 +1,24 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: md_5 <git@md-5.net>
+Date: Tue, 15 Apr 2014 10:48:35 +1000
+Subject: [PATCH] Check Skull canPlace
+
+
+diff --git a/src/main/java/net/minecraft/server/ItemSkull.java b/src/main/java/net/minecraft/server/ItemSkull.java
+index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
+--- a/src/main/java/net/minecraft/server/ItemSkull.java
++++ b/src/main/java/net/minecraft/server/ItemSkull.java
+@@ -0,0 +0,0 @@ public class ItemSkull extends Item {
+             }
+ 
+             if (!world.isStatic) {
++                // Spigot Start
++                if ( !Blocks.SKULL.canPlace( world, i, j, k ) )
++                {
++                    return false;
++                }
++                // Spigot End
+                 world.setTypeAndData(i, j, k, Blocks.SKULL, l, 2);
+                 int i1 = 0;
+ 
+--