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/proguard-project.txt

@@ -0,0 +1,20 @@
+# To enable ProGuard in your project, edit project.properties
+# to define the proguard.config property as described in that file.
+#
+# Add project specific ProGuard rules here.
+# By default, the flags in this file are appended to flags specified
+# in ${sdk.dir}/tools/proguard/proguard-android.txt
+# You can edit the include path and order by changing the ProGuard
+# include property in project.properties.
+#
+# For more details, see
+#   http://developer.android.com/guide/developing/tools/proguard.html
+
+# Add any project specific keep options here:
+
+# If your project uses WebView with JS, uncomment the following
+# and specify the fully qualified class name to the JavaScript interface
+# class:
+#-keepclassmembers class fqcn.of.javascript.interface.for.webview {
+#   public *;
+#}