Possibility to opt-out of a code-snippet

With the new laws regarding privacy, we have to give the user the possibility to opt-out of some tracking-codes.

I think we're not going to be the only ones with that issue using this module, so we'll provide a patch. With that patch you'll be able to give the user a link to opt-out of a specific code-snippet. When the link is clicked a cookie will be placed, which will be checked on server-side, and if set the code just will not be in the output.