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/0055-Allow-Disabling-of-1.6.3-Structure-Saving.patch

@@ -1,4 +1,4 @@
-From 21b153776a02cb6931e8186f666a3bb52567f0ea Mon Sep 17 00:00:00 2001
+From 7ac90b95f5e78b0cc8c73bcb29d6cf58e7ed74ab Mon Sep 17 00:00:00 2001
 From: md_5 <md_5@live.com.au>
 Date: Sat, 21 Sep 2013 12:33:09 +1000
 Subject: [PATCH] Allow Disabling of 1.6.3 Structure Saving
@@ -25,10 +25,10 @@ index 1eb87ae..b3c8101 100644
                  this.e = new PersistentStructure(this.a());
                  world.a(this.a(), (PersistentBase) this.e);
 diff --git a/src/main/java/org/spigotmc/SpigotWorldConfig.java b/src/main/java/org/spigotmc/SpigotWorldConfig.java
-index eb118c6..a4cdc7a 100644
+index aa639fe..3825bdf 100644
 --- a/src/main/java/org/spigotmc/SpigotWorldConfig.java
 +++ b/src/main/java/org/spigotmc/SpigotWorldConfig.java
-@@ -180,4 +180,16 @@ public class SpigotWorldConfig
+@@ -184,4 +184,16 @@ public class SpigotWorldConfig
          randomLightUpdates = getBoolean( "random-light-updates", false );
          log( "Random Lighting Updates: " + randomLightUpdates );
      }