ObjectModelNavigatorNamespaceActions.onClickRemoveAllSubcomponents...

... now seems to be working to a first approproximation. I think it would really be a good idea to move the logic for accessing extension points into ObjectStoreNamespace so that no client needs to rely directly on these details. In particular it's of no consequence to a client of an ObjectStore how component instances are internally represented by the store. What's more, I'm not 100% satisfied with the JSON syntax (e.g. I think I would like extension point collections to comprise a vector of records key: object as opposed to jsonTag: object). If no part of OMM depends on this implementation detail, then making this change will be easy.