Clarify the meaning of "parentId" property of elements

[matthewGEA]

Within the RFC 3.1.1 Required Object Metadata
ParentId: the ElementId of the parent object

The RFC is not clear about what relationship should be used to determine what elementID to place within the ParentID element.

Given the ParentID property is required metadata and that platforms MUST support Hierarchical/Organizational Relationships, my interpretation is that ParentID shall be the organizational parent of an element, of which there shall only be one parent possible. Other relationship types may have many-to-many implementations.

@jwise-mfg please confirm the intent and I can propose the clarification text.

[jwise-mfg]

ParentId is whatever organizational parent the platform wishes to organize an object within, it is separate from any other graph relationships. Whether or not the parent/child relationship is strong association (eg: composition) is also indicated separately with the IsComplext flag.
See: #160
@matthewGEA feel free to send a PR to the RFP itself to clarify, but it will go into the spec.