roxygenized docs from Lee's updates
now return NA if unsure of WKT validity (e.g. not a simple "POLYGON")
if server reports error, warn user if WKT invalid. Also "No occurrences" is now not an error
updated wkt check to accommodate NA return value from check_wkt
updated wkt checking: warn user on invalid/unrecognized wkt if results empty
version bump
minor doc typo fix