Add link to file in heading

[danielcompton]

trafficstars

When generating source, you can add links to the individual functions, but there isn't a top level link to go to the file itself. It would occasionally be handy to have this.

[cbui]

Do we want a link next to every single fn's view source link? Or do we want it at the top of a ns doc?

[danielcompton]

Top of ns doc is probably nicer.