Change map view to show "display name" rather than the attribute

[gfragiadakis]

In the list of attributes in the Map View, I would prefer we list the "display name" rather than the actual name of the attribute for legibility (e.g. "Cause of death" rather than "cause_of_death").

[graft]

I should note that since display_name is not always defined, Timur's default behavior (attribute_name.split(/_/).map(&:capitalize).join(' ')) might be a useful fallback here.