ISM_TRANSITION should inherit from LOCATABLE in the XSD since it needs a nodeID because of sibling ISM_TRANSITIONS

[ppazos]

Ref: https://github.com/openEHR/reference-models/blob/master/models/openEHR/Release-1.0.2/XSD/Content.xsd#L125-L131

Currently modeling tools like the AR are generating archetype_node_id for the ISM_TRANSITIONs, and that generates invalid paths in the RM since we can't store the nodeID in the ISM_TRANSITION.

I'll do a fix to my merged XSD https://github.com/ppazos/cabolabs-ehrserver/blob/master/xsd/Version.xsd
When the issue on the RM is solved, we can make the change on the official XSDs.

Raised a JIRA issue for that: https://openehr.atlassian.net/browse/SPECPR-222