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/dimens.xml

@@ -0,0 +1,7 @@
+<resources>
+
+    <!-- Default screen margins, per the Android Design guidelines. -->
+    <dimen name="activity_horizontal_margin">16dp</dimen>
+    <dimen name="activity_vertical_margin">16dp</dimen>
+
+</resources>

src/ui/android/res/values/strings.xml

@@ -1,8 +1,9 @@
 <?xml version="1.0" encoding="utf-8"?>
 <resources>
 
-    <string name="app_name">GFTranslator</string>
-    <string name="action_settings">Settings</string>
-    <string name="hello_world">Hello world!</string>
+    <string name="app_name">GF Translator</string>
+
+    <string name="microphone">Microphone</string>
+    <string name="switch_languages">Switch languages</string>
 
 </resources>

src/ui/android/res/values/styles.xml

@@ -0,0 +1,20 @@
+<resources>
+
+    <!--
+        Base application theme, dependent on API level. This theme is replaced
+        by AppBaseTheme from res/values-vXX/styles.xml on newer devices.
+    -->
+    <style name="AppBaseTheme" parent="android:Theme.Light">
+        <!--
+            Theme customizations available in newer API levels can go in
+            res/values-vXX/styles.xml, while customizations related to
+            backward-compatibility can go here.
+        -->
+    </style>
+
+    <!-- Application theme. -->
+    <style name="AppTheme" parent="AppBaseTheme">
+        <!-- All customizations that are NOT specific to a particular API-level can go here. -->
+    </style>
+
+</resources>