Updated Upstream (Paper)

Upstream has released updates that appear to apply and compile correctly

Paper Changes:
05cb10c56f Add repo for Velocity natives to dev bundle (#6536)
7bd7b18811 Configurable feature seeds (#6531)
ca708a0944 Updated Upstream (Bukkit/CraftBukkit/Spigot) (#6539)
f02d3d8989 flattener should try to render custom translations (#6540)
1276bd5039 Fixed layers from V2550 not being added to list (#6541)
a763f258da docs: remove Paper tool method for patch mods
20903fcf5e docs: drop table of contents; it's built into GH

patches/server/0128-Left-handed-API.patch

@@ -0,0 +1,27 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: William Blake Galbreath <Blake.Galbreath@GMail.com>
+Date: Mon, 30 Nov 2020 06:03:06 -0600
+Subject: [PATCH] Left handed API
+
+
+diff --git a/src/main/java/org/bukkit/craftbukkit/entity/CraftMob.java b/src/main/java/org/bukkit/craftbukkit/entity/CraftMob.java
+index 2386edf499cb292241f6ba60c1cdb46f2fe704ff..2f87513408972b7eed7fd0f3f94ac9799858f58a 100644
+--- a/src/main/java/org/bukkit/craftbukkit/entity/CraftMob.java
++++ b/src/main/java/org/bukkit/craftbukkit/entity/CraftMob.java
+@@ -135,4 +135,16 @@ public abstract class CraftMob extends CraftLivingEntity implements Mob {
+         return getHandle().getMaxHeadXRot();
+     }
+     // Paper end
++
++    // Purpur start
++    @Override
++    public boolean isLeftHanded() {
++        return getHandle().isLeftHanded();
++    }
++
++    @Override
++    public void setLeftHanded(boolean leftHanded) {
++        getHandle().setLeftHanded(leftHanded);
++    }
++    // Purpur end
+ }