Scan more than one Overdrive Library

[driscoll42]

Is your feature request related to a problem? Please describe.
Currently Library Scan only scans one Library at a time. I have access to multiple libraries on Overdrive and cannot scan both.

Describe the solution you'd like
Ideally Library Scan would scan multiple libraries and combine the results into one list. Presumably in some kind of for loop checking multiple libraries and merging them. I think being greedy would work (if found at L1, then skip checking L2, but only if available) but I could see some people wanting to see all the libraries the book is available at.

Describe alternatives you've considered
I can swap out the urls for the libraries for now which isn't a big deal.