Commands have been updated to use the busybox executable that
is installed via WA rather than relying on it already being in
PATH on the device as this would fail for devices that it was
not installed on.
list_or_* functions (e.g. list_or_string) will now always return a list,
however will accept lists or indivitual values. Also added a list_or()
generator function, similar to what already exists for list_of().
