02 filesystem questions + exercises

[k8hertweck]

These exercises could easily be expanded to include other tasks that are conceptual and not directly related to the project assignment. I would like to revise these once we've settled on exercises for other chapters, and have identified conceptually challenging things that pop up later in the book.

One big question I have is whether we'll be using the shell extensively in the rest of the book. This would inform whether we should include exercises explicitly about using those commands.

[lwjohnst86]

For your question, I don't envision using the shell much throughout the book. Maybe for doing some git commands since RStudio's Git interface only has pieces of the functionality.