Removing a resource should always remove all children

Invoking a remove op on a resource should always result in all child resources being properly removed.

1) Currently some resources reject a remove if children still exist. This behavior should be forbidden.

2) AbstractRemoveStepHandler should recursively remove children by adding steps invoking the remove op for them. This will ensure whatever MSC or capability registry changes the remove op handler for the children would normally make happen.

A driver for this is the new features related to cloning profiles and including profiles in other profiles. These increase the likelihood that users will wish to remove profiles, and to make that practical there needs proper recursive removal.