Add option for recursive search for wallappers

[rs-pro0]

I think making it default can be not the best idea but I think it should be an option like a checkbox. Implementation will be the same as in azote using find.

[nwg-piotr]

We already have plenty of checkboxes. I tend to add only what I find necessary.

[nwg-piotr]

It does not concern nwg-shell-config, if I understand well.