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/0018-Entity-Activation-Range.patch

@@ -1,4 +1,4 @@
-From f703353afd10357543bc579d91070a3e92496aea Mon Sep 17 00:00:00 2001
+From 825f177a357447c0542949b349e839fee21c50ce Mon Sep 17 00:00:00 2001
 From: Aikar <aikar@aikar.co>
 Date: Sun, 3 Feb 2013 05:10:21 -0500
 Subject: [PATCH] Entity Activation Range
@@ -457,10 +457,10 @@ index 0000000..db4c927
 +    }
 +}
 diff --git a/src/main/java/org/spigotmc/SpigotWorldConfig.java b/src/main/java/org/spigotmc/SpigotWorldConfig.java
-index 47d8421..f7c6166 100644
+index 49a5b7a..1d95207 100644
 --- a/src/main/java/org/spigotmc/SpigotWorldConfig.java
 +++ b/src/main/java/org/spigotmc/SpigotWorldConfig.java
-@@ -134,4 +134,15 @@ public class SpigotWorldConfig
+@@ -138,4 +138,15 @@ public class SpigotWorldConfig
          mobSpawnRange = (byte) getInt( "mob-spawn-range", 4 );
          log( "Mob Spawn Range: " + mobSpawnRange );
      }