Designer feature duplication should create an independant copy

Reproduction steps:

1. Create a Left Menu Entry and configure it (use whatever element, it is not relevant in the test, mine was using a nuxeo-search-form)
2. Go to the "Left menu Entry" entry, and duplicate your entry
3. In the duplicated entry, try to do modifications not linked to the element (e.g. modify the Label, Icon, order, or one of the filter)
4. Go back to the original entry: it also has been modified
5. Delete the original entry and go back to the duplicated one: everything should has been erased apart from the element and its configuration

Also applies with Actions or Document pages

EXPECTED

• Creating a duplicate should create an independant copy of the initial feature