Backport the ticket but instead of preventing the use of internal special properties, only warn on use of a reserved internal special property.

Want to prevent the use of internal properties when not needed.  The REST API should be the only path allowing the use of internal properties, so generally import and blip should not allow these to be set.  Needs additional design work to validate this assumption for all internal properties, and determine the right place in the stack to perform this check for import and blip, and any properties that should also be excluded for REST (e.g. _purged).