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/0071-Allow-Disabling-Zombie-Villager-Aggression.patch

@@ -1,4 +1,4 @@
-From 6b13883ffdd352eebd155c6d05c6ed7c3fa37c2f Mon Sep 17 00:00:00 2001
+From 5df9392ef7ee1760da1f9d62facd50b06cf7c4ec Mon Sep 17 00:00:00 2001
 From: Dylan Xaldin <Puremin0rez515@gmail.com>
 Date: Thu, 12 Dec 2013 18:05:03 -0600
 Subject: [PATCH] Allow Disabling Zombie Villager Aggression
@@ -28,10 +28,10 @@ index 6c6e03e..5c8b0a8 100644
      }
  
 diff --git a/src/main/java/org/spigotmc/SpigotWorldConfig.java b/src/main/java/org/spigotmc/SpigotWorldConfig.java
-index b207c02..ea447f9 100644
+index b9399ad..e7cb99d 100644
 --- a/src/main/java/org/spigotmc/SpigotWorldConfig.java
 +++ b/src/main/java/org/spigotmc/SpigotWorldConfig.java
-@@ -239,4 +239,11 @@ public class SpigotWorldConfig
+@@ -243,4 +243,11 @@ public class SpigotWorldConfig
  
          antiXrayInstance = new AntiXray( this );
      }