Add role info on user edit

[rgaudin]

User edition UI should explain the difference between the different roles and permissions to help choose, ie.:

• What is the motto/definition of each role
• Full List of available permissions with definitions
• What are the permissions associated to each role/user

[kelson42]

@rgaudin Not sure all of this should be (only?) visible at user edit, but yes it should be somehow clearly visible.

[stale[bot]]

This issue has been automatically marked as stale because it has not had recent activity. It will be now be reviewed manually. Thank you for your contributions.

[stale[bot]]

This issue has been automatically marked as stale because it has not had recent activity. It will be now be reviewed manually. Thank you for your contributions.