Perfect some aspect of directory-based profiles

[MrHedmad]

This essentially adds two things:

• Better error checking if profile files do not exist;
• The "touch on profile change" feature now re-touches all files and directories if a profile targets a directory instead of a file.

TODO

Before merging, tick all of these boxes:

• cargo test -- --include-ignored passes without errors or warnings.
• Documentation is updated that reflect these changes.
  • This PR changes nothing that is reflected in docs.
• @all-contributors is made aware of this PR.