Lack of screen reader support

[veinfors]

We need to make sure screen readers works equally well as in the old filter pane.

(Might require keyboard navigation to be improved to be able to test this properly - #81)

[johanlahti]

Current status: We support the most basic screen reader attributes, e.g. reading the label state ("A selected, B available" etc.) but we have to verify with a NVDA on a Win machine (unless there is a Mac version for it) and possibly fill some holes.

For instance, aria-selected seem not to work in Voice Over. Either, I'm missing something or this particular screen reader is not following the web standard.