Add context to Student Education Organization Association documentation

Based on discussions around the Student Education Organization Association demographic and identification elements, the following documentation updates have been suggested:

1. Update documentation for StudentEducationOrganizationAssociation to be "This association represents student information as reported in the context of the student's relationship to the Education Organization. Enrollment relationship semantics are covered by StudentSchoolAssociation."
2. Update the documentation for EducationOrganization to be "A reference to the Education Organization representing the context of the student information."

The intention is to clarify the StudentSchoolAssociation to be the primary enrollment record and that student data on StudentEducationOrganizationAssociation is within the context of that education organization.