Android: Greatly simplify MotionAlertDialog theming

Source/Android/app/src/main/res/drawable/dialog_round.xml

@@ -0,0 +1,12 @@
+<?xml version="1.0" encoding="utf-8"?>
+<shape xmlns:android="http://schemas.android.com/apk/res/android">
+    <solid
+        android:color="@android:color/white"/>
+    <corners
+        android:radius="28dp" />
+    <padding
+        android:left="4dp"
+        android:top="4dp"
+        android:right="4dp"
+        android:bottom="4dp" />
+</shape>