UnstructuredDataDependency: Rename "Root"

[HeyJoel]

The term "root entity" is used in both the UnstructuredDataDependency table and in the domain layer in RootEntityMicroSummary, given that these are both closely related I think we should look at the terms here. It might be that neither needs to use "root", and instead the relationship is defined but the name of the property the entity is connecting to e.g. UnstructuredDataDependency.RootEntityId could just be UnstructuredDataDependency.EntityId, where RelatedEntityId defines that relationship.

For RootEntityMicroSummary and ChildEntityMicroSummary, again I think it would be better to rename RootEntityMicroSummary to EntityMicroSummary and have ChildEntityMicroSummary layer on top the alternative behaviour / term, but it needs more investigation.

For now I have clarified in comments.