Overview of changes
- Add fedora-toolbox image definition for Fedora 31
- Add flatpak-xdg-utils to Fedoras 29 and 30
- Add manuals
- Add rm and rmi commands
- Be more informative when creating the working container
- Clarify the error message if the toolbox container is not found
- Don't create volumes in the image for bind mounts from the host
- Fix miscellaneous issues pointed out by https://www.shellcheck.net/
- Give access to /dev/bus for control transfers from USB devices
- Give access to removable devices and other temporary mounts
- Lots of Bash-isms removed for POSIX correctness
- Make the --image flag override the base toolbox image, as documented
- Make the spinner more efficient
- Restore documentation removed from the base Fedora images