add shadow to circlemarker

[emillipede]

current circlemarker	zeplin circlemarker

as a:
user

when I:
select a tree

I want to:
easily see which tree marker I selected

• add shadow
  - update format
  - - adjust marker size
  - for mobile users: expand touch radius (and maybe add marker clustering)

notes:

• the marker size for the "heritage" map view is currently independent of the other marker sizes
• the colors (and corresponding darker borders) in most views are automatically generated

sample CSS from zeplin:
Oval {
width: 14px;
height: 14px;
box-shadow: 0 2px 4px 0 rgba(0, 0, 0, 0.5);
border: solid 2px rgba(0, 0, 0, 0.5);
background-color: #f7bbfe;
}