Adding extpack via VBoxManage is totally confusing

[Ken Sharp]

The help file describes how to install the extpack graphically, and it's very simple. The explanation of the command line procedure isn't.

"To add a new extension pack, use VBoxManage extpack install <tarball>."

This had me looking for a tarball to download!

"file *.vbox-extpack" does reveal that it is a gzip tarball, but none of this is obvious at all.

[Frank Mehnert]

Thanks for the hint, will be fixed in the next maintenance release.