Check favicon sizes and formats

@christopheschwyzer @mariansollmann @dlondero 
Should we check our usage of *favicon* and other *splash*, *touch* or *tile* images before creating a lot of these for the new sites?

Summary: https://github.com/audreyr/favicon-cheat-sheet
PNG Favicon: http://www.jonathantneal.com/blog/understand-the-favicon/

[This article](http://www.jonathantneal.com/blog/understand-the-favicon/) says the `rel` attribute needs to be `shortcut icon` in all IEs. Is it wrong?

> In non-IE browsers, favicons can be served without the shortcut property.