Make AppCenter only included in debug builds.

Moves Flipper initialization to the same place as AppCenter.

app/src/release/java/com/majinnaibu/monstercards/init/AppCenterInitializer.java

@@ -0,0 +1,8 @@
+package com.majinnaibu.monstercards.init;
+
+import android.app.Application;
+
+public class AppCenterInitializer {
+
+    public static void init(Application app) {}
+}

app/src/release/java/com/majinnaibu/monstercards/init/FlipperInitializer.java

@@ -0,0 +1,9 @@
+package com.majinnaibu.monstercards.init;
+
+import android.content.Context;
+
+public class FlipperInitializer {
+
+    public static void init(Context ctx) {}
+
+}