Question bank: allow users to edit a question in a shared pool / group

How to reproduce:

• Question bank --> open a question item editor
• in the menu --> Share --> Share with pool
• Choose a pool and click "Select"

NOK: Question is shared with the pool but not editable by pool users. The step to allow editing is missing.

OK: A dialog is displayed where one can choose whether it is allowed for the pool users to edit the question or not. (For comparison: when using the button "Share" below the question items table, this decision can be made.)