Change station icon based on status

[Salacas]

Inside the map, show each station with an alert sign if there is an issue with it. Otherwise, the icon should be a green triangle.

Backend should implement its version of StationInfoRecord.station_info_gaps() inside https://github.com/demiangomez/Parallel.GAMIT/blob/master/classes/pyStationInfo.py in order to set the station status

[demiangomez]

We can probably use the same standard icons has in PG:
http://maps.google.com/mapfiles/kml/shapes/placemark_square.png -> in green or red if we are showing continuous vs survey data (determined by the number of observations: < 100 survey; > 100 continuous).
http://maps.google.com/mapfiles/kml/shapes/caution.png -> for a problem with metadata