Improve design of the uploading file for assignment of users to User groups in ADMM

Improve design of the uploading file for assignment of users to User groups.
2 ways of improvement :

 - Perform all relevant records of a uploading file. Today if 1 entry is wrong, all the file is rejected.

 - provide a report just after the load via pop up, with the following info : count of records OK, count of records Failed, and for each (OK and failed), the detail of the records. You can reuse the existing design in Construct, for the Loading file of "User release map".