Add Link reference in header to favicon

[paceaux]

src/template/partials/header.hbs does not contain a reference to the favicon

Gruntfile.js copies the favicon.ico file into a temporary directory while serving the site: https://github.com/sdl/dxa-html-design/blob/master/design/Gruntfile.js#L201

It also copies the file for a build.

However, without a hard reference to the favicon, a browser may cache an old favicon and use that instead.

Using <link rel="icon" href="http://www.yoursite.com/favicon.ico?" /> will help assure that browsers show the correct favicon: http://stackoverflow.com/questions/2208933/how-do-i-force-a-favicon-refresh

[bkoopman]

Not really sure about the use of the querystring there, that seems to make the browser load the favicon every request, which seems like needles overhead. But Agree that we should add the link tag for the favicon to the header indeed.

[paceaux]

The querystring was a typo, that's not necessary. Sorry about that.

[rpannekoek]

TSI-1948 (internal issue ID for tracking purposes)