Replace 'cad' key in package.yaml examples with generic 'files' key.

There is no point in having separate entries for CAD/CAM files and
general files. Images however stay in their own key.
Move CAD file from 'cad' key to 'files' key
Add loop that lists images, files, scripts etc for a package
Add some more functions
Move some functions from core/hm.py.

* Complete processFile to wrangle all ways to reference a file into a
single structure.
Move CAD files to 'files' key