As I noted in my comment in another issue, a few files are mostly software-dossier related but have a few functions/types related to packages. FileData and ClassInterface are the main examples. There are likely other files in drasil-code with bits of package-related functionality as well. I think it makes sense to extract these functions/types into a common file to help separate their purposes.

The only existing file that we could move these into is PackageFiles. It's a bit of a specific part of "package"-related stuff, so I'm torn on whether we should move more stuff here or just create a new file or new files. I'll look at it a bit more and add a comment with the direction I end up leaning.