Need for chaining link checks

[Nortamo]

Currently there are test to check for hidden files (#122 ), i.e files which don't have any links pointing to them. What would also be good to have is to have chaining link test.

So a file might have a link to it from another file, but is not accessible if there is no link to
the other file. At the moment we have no way of automatically checking this.

Working:
navbar -> f1 -> f2
we can access f2 normally

Broken:
navbar -> f1-> f2
we can't access f2 normally we need to manually look at f1.