Implement area selection for NASA OMI data

[aapopescu]

Similar approach to

#784

[leothomas]

Hi,

Just adding some detail on the request made to us by Nasa scientists working on the NO2 and CO2 datasets.

They would like the area selection + timeseries chart to be available for both the NASA OMI and NASA OMI DIFFERENCE datasets, as well as the MEAN CO2 and DIFFERENCE CO2 datasets.

Please let me know if there is anything I can do to support this.

Thanks!

[santilland]

To keep track of status:
After review for now we will wait to see if the API can be extended to accept a request for a time interval instead of a specific month. Evaluation of extension feasibility should be available before end of Mai.
NASA-IMPACT/covid-api#127