Move stuff into commons, rename PermissionObject, add more javadocs to api

common/src/main/java/me/lucko/luckperms/commands/SenderFactory.java

@@ -0,0 +1,30 @@
+package me.lucko.luckperms.commands;
+
+import java.lang.ref.WeakReference;
+
+public abstract class SenderFactory<T> {
+
+    protected abstract void sendMessage(T t, String s);
+    protected abstract boolean hasPermission(T t, String node);
+
+    public Sender wrap(T t) {
+        final SenderFactory<T> factory = this;
+        return new Sender() {
+            final WeakReference<T> cs = new WeakReference<>(t);
+
+            @Override
+            public void sendMessage(String s) {
+                final T c = cs.get();
+                if (c != null) {
+                    factory.sendMessage(c, s);
+                }
+            }
+
+            @Override
+            public boolean hasPermission(String node) {
+                final T c = cs.get();
+                return c != null && factory.hasPermission(c, node);
+            }
+        };
+    }
+}