Improvements to the user list and user info view

[alexAubin]

Related to YunoHost/yunohost#2153

• user list :
  • Add an "old key" icon in front of admins users
  • Add a list of badges for the groups each users are in
  • Sort the list with admins on top, then other users, sorted alphabetically (that's actually on the core side)
• user info :
  • Drop the intermediate, odd and unecessary "readonly" view
  • (Done but not tested..) Integrate the 'delete' button on the edit view
  • Some label / description / title tweaks
  • Split into 3 sections : main, email, password
  • Add the list of group and permissions of the user
  • Display mailbox usage
  • Ideally it should be possible to add / remove the user to / from groups from this view ... but I couldn't make it work with TagsSelectizeItem ... Ideally adding/removing group would also auto-update the permission list ... (We probably want the permission list to stay readonly because permissions are inherited from the groups (except for 'individual permissions' which should remain an exception))
  • Ideally, be able to manage ssh keys for the user

Current state is : a bit shaky ... but if that's good-enough we may merge it as is idk