Fully remove scarpet commands when apps are unloaded (#1452)

Using new Loader 0.14+ features

src/main/java/carpet/fakes/CommandDispatcherInterface.java

@@ -0,0 +1,5 @@
+package carpet.fakes;
+
+public interface CommandDispatcherInterface {
+    void carpet$unregister(String node);
+}

src/main/java/carpet/fakes/CommandNodeInterface.java

@@ -0,0 +1,5 @@
+package carpet.fakes;
+
+public interface CommandNodeInterface {
+    void carpet$removeChild(String name);
+}