Threading and rasterio datasets

[groutr]

Rasterio/GDAL dataset objects are not threadsafe. There are several places where FIM attempts to parallelize operations on rasterio datasets.

One such place is tools/overlap_inundation.py

The use of threading in this file and elsewhere needs to be carefully considered. This is especially important when writing to datasets.

Note: Ryan Grout knows a lot about this and it is recommended to ask him for more details and possible fixes.