Improve the file explorer

[caoimhebyrne]

At the moment, the file explorer is quite limited, and is missing a lot of basic functionality, like:

• Creating folders
• File/folder context menus
  • Creating new files
  • Creating a sub-folder
  • Deleting a file
  • Renaming a file
  • etc.

[caoimhebyrne]

As a note, this was originally meant to be completed in #2, but the PR quickly became stale and we should have a more expressive way to handle file actions.