Update upstream B/CB/S

Adds /paper command for reloading the paper config.
Closes GH-639

Per-world config logging has been removed in favor of all or nothing
logging for all paper settings. I don't believe it was used enough to
warrant maintaining. If this is not the case it should be possible to
re-add it.

Spigot-Server-Patches/Undead-horse-leashing.patch

@@ -6,7 +6,7 @@ Subject: [PATCH] Undead horse leashing
 default false to match vanilla, but option to allow undead horse types to be leashed.
 
 diff --git a/src/main/java/com/destroystokyo/paper/PaperWorldConfig.java b/src/main/java/com/destroystokyo/paper/PaperWorldConfig.java
-index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
+index 9987a5c7a..0873febb6 100644
 --- a/src/main/java/com/destroystokyo/paper/PaperWorldConfig.java
 +++ b/src/main/java/com/destroystokyo/paper/PaperWorldConfig.java
 @@ -0,0 +0,0 @@ public class PaperWorldConfig {
@@ -20,7 +20,7 @@ index 0000000000000000000000000000000000000000..00000000000000000000000000000000
 +    }
  }
 diff --git a/src/main/java/net/minecraft/server/EntityHorseAbstract.java b/src/main/java/net/minecraft/server/EntityHorseAbstract.java
-index 0000000000000000000000000000000000000000..0000000000000000000000000000000000000000 100644
+index d74ccd68d..3416c7a7d 100644
 --- a/src/main/java/net/minecraft/server/EntityHorseAbstract.java
 +++ b/src/main/java/net/minecraft/server/EntityHorseAbstract.java
 @@ -0,0 +0,0 @@ public abstract class EntityHorseAbstract extends EntityAnimal implements IInven