Theme Support

1) Broke out the UI elements of the major Activites into stylable
   attributes.

2) Created a 'light' and 'dark' theme for the newly stylable attrs.

3) Touched up some of the UI spacing.

4) Implemented dynamic theme switching support.

src/org/thoughtcrime/securesms/util/Util.java

@@ -184,7 +184,6 @@ public class Util {
     return new String(bout.toByteArray());
   }
 
-
   //  public static Bitmap loadScaledBitmap(InputStream src, int targetWidth, int targetHeight) {
   //    return BitmapFactory.decodeStream(src);
   ////  BitmapFactory.Options options = new BitmapFactory.Options();