Disable use of default design part. Require user to explicitly specify design part.

[darrenm]

Provide a configuration item that would prevent any reliance on default design parts.  This would require the user to specify a design part instead of merely accepting the default.  Users often do not specify a design part, which results in new items getting incorrectly related to the wrong design part.  We are able to prevent this indirectly because requests can't be created on the default design part because of role privileges.  A request is automatically related to the same design part as the new item, so this prevents delivery of the new item.  This will not work in any stream with CM rules disabled, though.