Allow minor versioning by allowing stats to be run without raster generation

[robbibt]

Currently, running the DEACL statistics code requires the user to specify a single output_name string that was originally used to generate the DEACL rasters. This is used in the file names of the output vector files, which means that all runs of the stats code will overwrite each other until a new version of rasters (with a new output_name) is generated.

To avoid this and allow multiple versions of the vector files to be generated from a single raster generation, the DEACL stats code should support both an input input_name (e.g. v0.3.0), and an output output_name (e.g. v0.3.1).