CRS parsing is not correctly handled for CSV files

[giohappy]

@mattiagiupponi maybe it's a regression but from my tests the upload of CSV is always failing due to exceptions thrown inside BaseVectorFileHandler.identify_authority().

With CSV files layer.GetSpatialRef() returns always None, so both the try and the exception handler will fail at retrieving the CRS.
I think BaseVectorFileHandler.identify_authority() should be overridden by the CSV handler and, for simple geom fields (lat/lon) the CRS will be forced to EPSG:4326

[mattiagiupponi]

For the CSV is indeed force to EPSG:4326
In this case with the introduction of this fix #233. For the CSV that checks is not useful since the authority is extracted later. We can justlet the CSV skip that part. Once the CSV is validated we are good to go