Add three status icon for the hamburger menu:
* hamburger_menu.svg: The typical hamburger menu. Taken from
https://commons.wikimedia.org/wiki/File:Hamburger_icon.svg, which is
in the public domain.
* hamburger_menu_update_error.svg: A hamburger menu with a red
notification bubble on the top right corner.
* hamburger_menu_update_success.svg: A hamburger menu with a green
notification bubble on the top right corner.
