Add favicon & Apple Touch icons

References favicon and apple-touch-icon files. I've written it so that the browser searches for favicon.png, but it could be argued that for compatibility reasons it is perhaps better to simply leave off the html reference and instead just place a favicon.ico (must be ico) file in the root - this tends to be the default a browser (even prehistoric browsers) look for - it can also help prevent weird 404 issues. So your choice!

The apple touch icon references just a single .png file, some say add multiple sizes, I say no, you are wrong! Off the top of my head I think it's best to upload an image 128 x 128 - this'll cover all Apple touch devices.