Add a class to links, to allow theming

Hi,

Having a class on Publish / Unpublish tabs could allow us a special theming, allowing more accessibility (this tab is an action, not a screen, so theming it differently could help people understand it better (or position the link differently).

You'll find attached a patch doing just that (using "options" to add a class to the link).
Note: for now, this won't do anything, because of #1043906: Document how to possible to add link options when defining local tasks and actions, but as soon as this core bug is fixed, the module could benefit for it directly.