Tweaks to command system to allow setting executors via plugins (no more ambiguous onCommand in plugins)

By: Dinnerbone <dinnerbone@dinnerbone.com>

paper-api/src/main/java/org/bukkit/command/CommandMap.java

@@ -31,4 +31,12 @@ public interface CommandMap {
      * Clears all registered commands.
      */
     public void clearCommands();
+
+    /**
+     * Gets the command registered to the specified name
+     *
+     * @param name Name of the command to retrieve
+     * @return Command with the specified name
+     */
+    public Command getCommand(String name);
 }