Add role='application' to FeatureGroup <g> element

[prushforth]

Fixes #423

[Malvoz]

It seems that NVDA announces everything on the page after pressing a feature to open a popup. At this point, I'm starting to think we're doing the user a disservice by not just making the entire map role="application".

[prushforth]

Ok I'll have a look at that when I get a chance.

[Malvoz]

Maybe we should just go ahead and replace role="region" of the maps (in web-map.js as well) with role="application" (and close out #274).

I'll go ahead and do some testing with that approach, see how it behaves.

[prushforth]

For some reason I didn't experience NVDA reading the whole page. I only tried it on the restaurant page though.