Add related contact to offices index

Displays related_contact &/or general inquiries contact info on offices index page.

- Moves contact-us code into macro for reuse here. (Macro currently still lives in contact-us directory)
- Uses single query to fetch both related_contact & 'general_inquiries'. May need to change if there is a preference in display order.
The contacts section of the design shows a listing for `general-inquiries` as well as for the optional office-specific contact, so I'm building a query that searches for both. I suppose this could be an either/or proposition -- show `general-inquiries` only if no office_related contact has been specified -- but it might be helpful to have the general contact info in any case.