Add new Android voice translator sample app

This adds a simple voice translator Android app that uses
the JNI bindings to the PGF C runtime.

Caveats:

- Since the C runtime doesn't compile for Android right now,
  I've bundled an old copy, along with its Java bindings.
  That should be removed once the C runtime compiels for Android
  again.

- Adding an automated build would be nice.

- Replacing the grammar requires editing a Java file, that should 
  really be more dynamic.

src/ui/android/res/values-sw720dp-land/dimens.xml

@@ -0,0 +1,9 @@
+<resources>
+
+    <!--
+         Customize dimensions originally defined in res/values/dimens.xml (such as
+         screen margins) for sw720dp devices (e.g. 10" tablets) in landscape here.
+    -->
+    <dimen name="activity_horizontal_margin">128dp</dimen>
+
+</resources>