Create MetaEd DSL for the proposed model

From comment on 1867

Based on a suggestion by Audrey Shay, the proposed solution is provided in
the attached StudentAssessmentEducationOrganizationAssociation Plus V4.xlsx

Add the following optional attributes to StudentAssessment that would be written by the assessment vendor:
A new optional reference ReportedSchool to be used when the assessment vendor has the unique Id for the school
A new optional string attribute ReportedSchoolIdentifier
Add a new entity StudentAssessmentEducationOrganizationAssociation would optionally be used by the EdOrgs to write the definitive association(s) for administration, enrollment, or attribution, if desired.