(desktop) Top ribbon Map route should depend on redux state

[wbazant]

We should be able to e.g. navigate from /locations/new to /about and back. Restore map view and context of what is happening - e.g. viewing or editing the location.

In the #419 PR I added similar behaviour on mobile, so we can go to settings and back -see src/components/mobile/Tabs.js.

This will also enable #421 proposal to move settings into top ribbon.

[wbazant]

Not needed for #421 but would still be a small enhancement.

Note that we don't want to / don't need to put the view in e.g. the /about URL - just reconstructing the target route from redux states will work.