Add settings page

This pull request add a new settings page accessed by an icon on the top left corner.
This new settings page currently only have two settings:
 * Download location: Set the movie download location (default: system temporary folder)
 * Auto clear cache: Uncheck it to prevent the removal of the video file after the movie is watched

I added a new App.settings object that manage user settings in the localstore as well. This feature was requested by many of my friends, hopefully it will be usefull to the upstream.

Preview:
![image](https://f.cloud.github.com/assets/1420974/2418652/2c971ffc-ab49-11e3-8893-f34f3a2855f9.png)