Handle multiple datums when converting UTM to lat/lon in RAPlots.csv

[maggieklope]

Some records in RAPlots.csv's have the datum NAD83, while others have WGS84. This will affect how we convert the 'UTMN_final' and 'UTME_final' columns to lat/lon.

Records in RAPlots.csv use different geodetic datums NAD83, WGS84, and NAD27. Right now, the code assumes all records are NAD83, but we will need to adapt it to use the correct CRS/EPSG code depending on what is in the GPS_datum column.

Finally, we need to make sure that the values that to into PlotObservation's realLatitude and realLongitude are all in WGS84