Creating a new entity from a metadata URL does not do an import

[relaxnow]

• [ ] Import from metadata url doesn't work for creating new entities.
• [ ] Import from metadata XML doesn't work for creating new entities.
• [ ] When I create a new entity I do not see it in the list, trying to create again suddenly shows me the entity along with an error that it already exists.
• [ ] when I want to create a new entity and do an import from a metadata URL that contains only a single entity I should not have to specify the entityId.
• [ ] the UI here is really bad. A button shows and hides the create is non intuitive. I would expect something like what follows. And the "Create" button is in the exact same style and off to the right.

[thijskh]

The first issue is #337. Leaving open because of the other relevant issues.