ACL user and group picker: finish the implementation in the administration center

The new ACL user and group picker have not been implemented yet in the Administration Center.

There are several places where we still have ugly badly resized user and group pickers.

• For example while adding new users to a group (screenshot 1)
• or in all the rules interfaces (screenshot 2)

Could we rapidly remove such bad JSP (at the place of trying to fix them for the beta) and replace them by the new user and group picker (as it is already the case for ACL on categories, portlets, etc...) so that we could have only one single way of selecting a user or a group troughout the whole admin center.