v0.4.168

feat: a Left out tab in Backups, for the folders no backup copies (#168)

* feat: a Left out tab in Backups, for the folders no backup copies

One list for the box, one folder per line: what an app mounts from inside one
of them is left out of every backup. The field stays closed until the list has
loaded, so a failed load cannot be saved as an empty list.

* fix: say which path to write, and never take a missing list for an empty one

The help said to write the path as the app mounts it, which reads as the path
inside the container; it now asks for the folder's path on the box, and says
that a larger folder holding it is left out whole. The field is closed while
the list is saved, and an answer with no list in it is a failed load.