Cleanup Bookmarks, History, and SavedPages screen

- Redesigned bookmark thumbnail view
- Custom ImageView to scale the thumbnail properly
- Fix column count in bookmark expandable view
- Disable GroupView if we have only one account in bookmark

Change-Id: I2fccae50b9e96c909744bd5c7d0af7b373136c54
diff --git a/AndroidManifest.xml b/AndroidManifest.xml
index 2ede78a..87175fe 100644
--- a/AndroidManifest.xml
+++ b/AndroidManifest.xml
@@ -237,7 +237,8 @@
                   </intent-filter>
         </activity>
 
-        <activity android:name="ComboViewActivity">
+        <activity android:name="ComboViewActivity"
+                  android:theme="@style/ComboViewTheme">
         </activity>
 
         <!-- Bookmark thumbnail homescreen widget -->