Add "description" to docs for proximity views

[ccao-jardine]

Let's add descriptions for anything that's missing a description in proximity.vw_pin10_proximity and proximity.vw_pin10_proximity_fill. I like the current convention of having a brief description as well as the source. As an example, here's the description for nearest_golf_course_dist_ft:

Nearest cemetery distance (feet).

Cemetery data sourced from Cook County GIS

Just looking to hew as close to our current conventions as possible. Columns missing descriptions:

nearest_grocery_store_data_year
nearest_road_arterial_name
nearest_road_arterial_daily_traffic
nearest_road_arterial_speed_limit
nearest_road_arterial_surface_type
nearest_road_arterial_lanes
nearest_road_arterial_dist_ft
nearest_road_arterial_data_year
nearest_road_collector_name
nearest_road_collector_daily_traffic
nearest_road_collector_speed_limit
nearest_road_collector_surface_type
nearest_road_collector_lanes
nearest_road_collector_dist_ft
nearest_road_collector_data_year
nearest_road_highway_name
nearest_road_highway_daily_traffic
nearest_road_highway_speed_limit
nearest_road_highway_surface_type
nearest_road_highway_lanes
nearest_road_highway_dist_ft
nearest_road_highway_data_year