Now possible to "protect" front-end routes with permissions

Ideally the router would have done all the dirty work, but with currently there seems to be no way to wrap a route handler, so the permission branching will have to be done on a per-page basis, at the handler level. I've tried to centralize and simplify that process as much as possible with mixins and wrappers. I protected the AdminEditProfile route as an example.

There is currently a small rendering issue when a page access is denied and we navigate to the homepage, it seems like a React bug. (It could well be already be fixed in more recent versions...)

Addresses https://github.com/my-koop/service.website/issues/157