[Tools] Provide an "(un)installer option" in pamusb-conf for pamusb-keyring-unlock-gnome

[mcdope]

Provide an "(un)installer option" in pamusb-conf.

That option should...

• create/remove the keyfile and chmod it
• create/remove the .desktop file
• disable/enable autostarting gnome-keyring-daemon so we don't need to wait and kill and everything... (todotodo: check if possible)

Originally posted by @mcdope in https://github.com/mcdope/pam_usb/issues/11#issuecomment-974923472

[mcdope]

Guess if the pinentry stuff is merged, this should also be done for that.