Support WKT output in CSV Formatter

[allenj]

Is your feature request related to a problem? Please describe.
The current CSV Formatter only supports points. If my collection uses other geometry types these aren't included in the CSV output.

Describe the solution you'd like
Output geometries in WKT

Describe alternatives you've considered
Retain the x and y columns and include a separate "geometry" or "wkt" column so x, y columns can be utilized by other tooling.

Additional context
WKT contains commas so WKT will need to be quoted. Also, it might be beneficial to specify within a resource whether or not to include WKT, x/y coordinates, or nothing.