fix: links not working when controls are disabled

This is my fix for links not working when controls are disabled. The reason is that the following isn't run:

- collect all navigation elements
- attach/remove event handlers to navigation elements
- update control elements (whether they are available or not)

Now all this code runs unconditionally. The dedicated control elements in the lower right are still created, but existing code turns them off, if `config.controls` is `false`:

    dom.controls.style.display = ( config.controls && dom.controls ) ? 'block' : 'none';

This is the very first stuff I've done with HTML and JS, so be extra careful. I've tested it with my presentation and it works as intended with controls `true`/`false`.