Allow plugins to use SLF4J for logging

SLF4J is a commonly used abstraction for various logging frameworks
such as java.util.logging (JUL) or Log4j. Currently, plugins are
required to do all their logging using the provided JUL logger.
This is annoying for plugins that target multiple platforms or when
using libraries that log messages using SLF4J.

Expose SLF4J as optional logging API for plugins, so they can use
it without having to shade it in the plugin and going through
several layers of logging abstraction.

Spigot-API-Patches/Allow-plugins-to-use-SLF4J-for-logging.patch

@@ -0,0 +1,52 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Minecrell <dev@minecrell.net>
+Date: Thu, 21 Sep 2017 16:33:12 +0200
+Subject: [PATCH] Allow plugins to use SLF4J for logging
+
+SLF4J is a commonly used abstraction for various logging frameworks
+such as java.util.logging (JUL) or Log4j. Currently, plugins are
+required to do all their logging using the provided JUL logger.
+This is annoying for plugins that target multiple platforms or when
+using libraries that log messages using SLF4J.
+
+Expose SLF4J as optional logging API for plugins, so they can use
+it without having to shade it in the plugin and going through
+several layers of logging abstraction.
+
+diff --git a/pom.xml b/pom.xml
+index ad385f45..b83c6eb1 100644
+--- a/pom.xml
++++ b/pom.xml
+@@ -0,0 +0,0 @@
+             <scope>compile</scope>
+         </dependency>
+ 
++        <!-- Paper - Add SLF4J -->
++        <dependency>
++            <groupId>org.slf4j</groupId>
++            <artifactId>slf4j-api</artifactId>
++            <version>1.7.25</version>
++            <scope>compile</scope>
++        </dependency>
++
+         <!-- testing -->
+         <dependency>
+             <groupId>junit</groupId>
+diff --git a/src/main/java/org/bukkit/plugin/Plugin.java b/src/main/java/org/bukkit/plugin/Plugin.java
+index c4e22c62..02670254 100644
+--- a/src/main/java/org/bukkit/plugin/Plugin.java
++++ b/src/main/java/org/bukkit/plugin/Plugin.java
+@@ -0,0 +0,0 @@ public interface Plugin extends TabExecutor {
+      */
+     public Logger getLogger();
+ 
++    // Paper start - Add SLF4J logger
++    default org.slf4j.Logger getSLF4JLogger() {
++        return org.slf4j.LoggerFactory.getLogger(getLogger().getName());
++    }
++    // Paper end
++
+     /**
+      * Returns the name of the plugin.
+      * <p>
+--

Spigot-Server-Patches/Include-Log4J2-SLF4J-implementation.patch

@@ -0,0 +1,24 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Minecrell <dev@minecrell.net>
+Date: Thu, 21 Sep 2017 16:33:35 +0200
+Subject: [PATCH] Include Log4J2 SLF4J implementation
+
+
+diff --git a/pom.xml b/pom.xml
+index fa726851b..647b2c619 100644
+--- a/pom.xml
++++ b/pom.xml
+@@ -0,0 +0,0 @@
+         </dependency>
+ 
+         <!-- Paper - Add additional Log4J dependencies -->
++        <dependency>
++            <groupId>org.apache.logging.log4j</groupId>
++            <artifactId>log4j-slf4j-impl</artifactId>
++            <version>2.8.1</version>
++            <scope>runtime</scope>
++        </dependency>
+         <dependency>
+             <groupId>org.apache.logging.log4j</groupId>
+             <artifactId>log4j-iostreams</artifactId>
+--