Most libraries use our standard Terms of Service, but some libraries have negotiated an alternate Terms of Service. We need to make two changes to accommodate these libraries: one small, one not so small.

The small one is that the copy that the library registry sends needs to be changed from "By checking this box you agree to the SimplyE Terms of Service for Partner Libraries." to something like "By checking this box you agree to the SimplyE Terms of Service for Partner Libraries, or other terms by prior agreement with NYPL."

The bigger one is that the work done in https://jira.nypl.org/browse/SIMPLY-2279 needs to be expanded. The link used in the T&C footer for a library needs to come from a site-wide configuration setting that (maybe this next bit can wait) can be overridden on a per-library basis. We can't hard-coded it anymore.