Tweak the color and opacity of the grid cell borders

[pleary]

It is a known problem that when viewing the grids with the 'Map', not 'Satellite', map style that green grids can be very hard to see over green parks and conservation areas. We should restore the white grid border opacity to 1. Additionally see what other changes can be made to increase visibility of grids (using different border colors for different grid colors, using custom map styles, etc.). Just keep in mind the map/satellite toggle which dramatically changes visibility concerns.