Allow the user to add new taxonomy term from the add product form

Currently, there is no way to add a new taxonomy term (catalog category, product attribute...) from the add product form.

We would ideally have :

1. A link under each taxonomy reference field to add new one that will redirect to the add new term page on the corresponding vocabulary
2. Redirect the user to the same form with the list up to date displaying the new term

There might exist some modules that handle that feature.