Curriculums don't export/import correctly because the export is a node reference to a node ID rather than a UUID

Problem/Motivation

Curriculums don't export/import correctly because the export is a node reference to a node ID rather than a UUID

Proposed resolution

Help get entityreference module to support UUIDs. Then update our implementation of entity references to use UUIDs.

Remaining tasks

1. #1225198 Get entityreference module to support UUIDs
2. update our implementation of entity references to use UUIDs

User interface changes

none

API changes

none