new harvester to process AERONET data

The dataset is part of the SRS OC LJCO subfacility. The
harvester reads a .lev2 (csv) file from a public folder
downloaded everyday by a python script. see:
https://github.com/aodn/data-services/blob/master/SRS/SRS_OC_LJCO_AERONET/downloadAeronetData.py