Bug 22600: Add 'api' to interface types and set appropriately

Bug 22600: Add 'api' to interface types and set appropriately

This patch adds 'api' as a valid interface and sets it appropriately for
both the new REST api and previous /svc/ api's.  Handling to keep the
interface of a logged in session is included such that if the OPAC or
Intranet use the API's internally via a Cookie we will maintain the
interface throughout the session.

Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Josef Moravec <josef.moravec@gmail.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>