#JC-1834 Updated favicon removing rel="shortcut" as it's obsolete now.

WHATWG [1] explains that 'shortcut' was valid for historical reasons, but
now W3C Validator [2] complains about it, so we need to remove it:

> For historical reasons, the icon keyword may be preceded by the keyword
> "shortcut". If the "shortcut" keyword is present, it must be come
> immediately before the icon keyword and the two keywords must be separated
> by only a single U+0020 SPACE character."

[1] http://www.whatwg.org/specs/web-apps/current-work/multipage/links.html#rel-icon
[2] http://validator.w3.org/