Add SCOAP3 API server configuration

* Adds new configuration variables: CFG_SCOAP3_API_SERVER,
  CFG_SCOAP3_ONLY_MEMBERS_ACCESS

* CFG_SCOAP3_ONLY_MEMBERS_ACCESS - restricts access to search services
  if user is not logged in or doesn't provide key in search query.

* CFG_SCOAP3_API_SERVER - always sets the output format as XM.