Dark theme fixes.

1) Make the conversation background all black with no column.

2) Fix the font color on identity key review.

res/layout/identity_key_view.xml

@@ -33,8 +33,7 @@
               android:layout_alignTop="@id/contact_photo_frame"
               android:layout_toRightOf="@id/contact_photo_frame"
               android:layout_alignWithParentIfMissing="true"
-              android:ellipsize="marquee"
-              android:textColor="#000000"/>
+              android:ellipsize="marquee"/>
 
     <TextView android:id="@+id/fingerprint"
               android:layout_width="wrap_content"

res/values/themes.xml

@@ -36,7 +36,7 @@
         <item name="conversation_list_item_background_selected">@drawable/list_selected_holo_dark</item>
         <item name="conversation_list_item_count_color">#66dddddd</item>
 
-        <item name="conversation_card_background">#ffdddddd</item>
+        <item name="conversation_card_background">@color/black</item>
         <item name="conversation_background">@color/black</item>
         <item name="conversation_text_primary_color">@color/abs__primary_text_holo_dark</item>
         <item name="conversation_text_secondary_color">#ffcccccc</item>