Investigate the addition of an endpoint for collections to allowing adding new members without republishing the entire collection

[mparsons-ce]

This is a backlog request for now.
The workflow would be:

• the collection must have been previously published
• an append/addMember endpoint could be used to add additional collection members
• as well perhaps the ability to append to the hasMember property of a collection (list of URIs)
• the process would check if the CollectionMember (based on the ProxyFor URI) or HasMember already exists

It would also be useful to have a removeMember endpoint.

[siuc-nate]

@mparsons-ce Is this still a valid/relevant issue?