Output FIM Rasters have nodata borders

[ar-siddiqui]

Output FIM Rasters have no data borders, which should be trimmed, they look like an artifact of RAS. This slows down flows2fim and occupies unnecessary storage.

The pink box is the extent of the raster

First, we should try to see if there is a simple upstream fix of where this issue is arriving from, but if this is indeed RAS. Then rasterIO/gdal python need to be used to fix this.

https://gis.stackexchange.com/questions/45159/finding-minimum-bounding-extent-of-given-pixel-value-within-raster/149511#149511