Revert previous change to clear chunk list on the end of each tick, make it configurable instead.

Whilst the new behaviour was technically correct as it prevented the possibility of the chunk tick list actually increasing over time, it introduced a few issues, namely the fact that it slowed growth to unreasonable levels, and interfered with the values which server admins have finally tuned, and come to enjoy over the last few years.
If it is absolutely essential that growth be halted and ticking reduced as much as possible, the config option is there for power users.
If we wish to 'fix' this by default in the future, a new chunk ticking algorithm, which actually has meaningful config options should be designed.

By: md_5 <git@md-5.net>

CraftBukkit-Patches/0056-Item-Despawn-Rate.patch

@@ -1,4 +1,4 @@
-From dd603179f1246321346cd3394a2fb2a6f762e92a Mon Sep 17 00:00:00 2001
+From 271b8162947d0cb71d237b42f39ca03135732626 Mon Sep 17 00:00:00 2001
 From: md_5 <md_5@live.com.au>
 Date: Sun, 22 Sep 2013 19:10:53 +1000
 Subject: [PATCH] Item Despawn Rate
@@ -18,10 +18,10 @@ index 08b9ac8..8ea7abc 100644
                  if (org.bukkit.craftbukkit.event.CraftEventFactory.callItemDespawnEvent(this).isCancelled()) {
                      this.age = 0;
 diff --git a/src/main/java/org/spigotmc/SpigotWorldConfig.java b/src/main/java/org/spigotmc/SpigotWorldConfig.java
-index a4cdc7a..0b4e527 100644
+index 3825bdf..72aabff 100644
 --- a/src/main/java/org/spigotmc/SpigotWorldConfig.java
 +++ b/src/main/java/org/spigotmc/SpigotWorldConfig.java
-@@ -192,4 +192,11 @@ public class SpigotWorldConfig
+@@ -196,4 +196,11 @@ public class SpigotWorldConfig
              log( "*** WARNING *** Please use this option with caution, SpigotMC is not responsible for any issues this option may cause in the future!" );
          }
      }