makeLinkEnabler does not allow marking specific links as "normal" links

In the [the EDPOP vre](https://github.com/UUDigitalHumanitieslab/EDPOP), we have certain internal links in the UI that are not handled by the SPA but instead by the backend. There are also a number of `` elements that act like buttons (they have `#` as their anchor and they include the `role="button"` property). I don't see a way in `makeLinkEnabler` to exclude specific links. I would propose the following:

* Exclude `` elements with `class="backbone-util-no-spa"` (better suggestions welcome)
* Exclude `` elements with `role="button"`, because they should never act as links

@jgonggrijp : if you agree, I will create a pull request for these changes.

Start by locating the makeLinkEnabler implementation and inspect how it selects anchor elements for SPA handling. Exclude links with class="backbone-util-no-spa" and links with role="button", then verify that these elements are left for normal backend or button behavior while other links remain enabled.

Written by the indexing model from the issue text.