Add "Show List" button to main map page

[salvatoto]

For communities with a high density of shops it's become difficult to navigate businesses. A button on the main map page that that brings up a basic list of all the businesses in the map region - or in the larger community the current map region is part of - would be useful. The list should be sorted by type of business in some way.

We should re-use CommunityDetailView for this as that view shows a list of businesses and should be sorted better as well.