The selection mechanism of Tabulator was getting in the way of having nice
navigation, as it would deselect (i.e. nav to "/") before selecting the
next job (i.e. nav to "/jobs/{job-id}").
The active job is now determined by the URL and thus handled by Vue Router.
Clicking on a job simply navigates to its URL, which causes the reactive
system to load & display it.
It is still intended to get job selection for "mass actions", but that's
only possible after normal navigation is working well.
Add a bar for "job actions", i.e. buttons that do something with the
selected job(s).
Just has one button, and it doesn't do much either, but at least the
framework for these things is here.
