allow setting tiff SoftwareTag, DocumentNameTag, ImageDescTag #3500

There's a number of tiff tags that currently can not be written to geotiff in Geotrellis.
For instance: SoftwareTag, DocumentNameTag, ImageDescTag
These are already defined here:

The request is to either add explicit support for these tags, or to allow a more generic way to customize the tags that are written so that we can add any tag.