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/DynamicTheme.java

@@ -0,0 +1,61 @@
+package org.thoughtcrime.securesms.util;
+
+import android.app.Activity;
+import android.content.Context;
+import android.content.Intent;
+import android.os.Build;
+import android.preference.PreferenceManager;
+
+import org.thoughtcrime.securesms.ApplicationPreferencesActivity;
+import org.thoughtcrime.securesms.R;
+
+public class DynamicTheme {
+
+  private int currentTheme;
+
+  public void onCreate(Activity activity) {
+    currentTheme = getSelectedTheme(activity);
+    activity.setTheme(currentTheme);
+  }
+
+  public void onResume(Activity activity) {
+    if (currentTheme != getSelectedTheme(activity)) {
+      Intent intent = activity.getIntent();
+      intent.addFlags(Intent.FLAG_ACTIVITY_NO_ANIMATION);
+
+      activity.startActivity(intent);
+      if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.ECLAIR) {
+        OverridePendingTransition.invoke(activity);
+      }
+
+      activity.finish();
+      if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.ECLAIR) {
+        OverridePendingTransition.invoke(activity);
+      }
+
+    }
+  }
+
+  public static int getSelectedTheme(Context context) {
+    String theme = PreferenceManager.getDefaultSharedPreferences(context)
+                                    .getString(ApplicationPreferencesActivity.THEME_PREF, "light");
+
+    return getSelectedTheme(theme);
+  }
+
+  public static int getSelectedTheme(String theme) {
+    if (theme.equals("light")) {
+      return R.style.TextSecure_LightTheme;
+    } else if (theme.equals("dark")) {
+      return R.style.TextSecure_DarkTheme;
+    }
+
+    return R.style.TextSecure_LightTheme;
+  }
+
+  private static final class OverridePendingTransition {
+    static void invoke(Activity activity) {
+      activity.overridePendingTransition(0, 0);
+    }
+  }
+}