Add additional settings to define which ORCiD service is used

Created by: pmather

The ORCiD service has available a sandbox and production service. The one used is determined by various URLs assigned to ORCID_*_URL environment variables, which define API endpoints. If these environment variables are unset then they default to the ones used by the sandbox service.

This change extends the settings that may be assigned in config/application.yml. The "orcid" gem uses this file to set ORCiD-related environment variables. We, in turn, derive the actual value set from the "orcid" key in config/secrets.yml.

This will allow the application to use the sandbox or production ORCiD service.