Adding and removing users from usergroup

As Administartor i want to be able to add and remove users from usergroups

1. User group page contains input for search for users and table of users for this user group with "Username" and "Email" columns.
2. Deleting users:
   • when administrator hovers user row in table icon "Remove user from group" appears;
   • after clicking this icon confirmation popup with text "Are you sure you want to remove user from group" and buttons "OK" and "Cancel" appears;
   • if administartor presses "OK" - user removes from group, if "Cancel" - popup closes, user isn't remove from group.
3. Adding users:
   • adding users performs via search users input;
   • when administartor typing in search input after 2 symbols autocomplete list is showing;
   • search performs by username and email which are displaying in autocomplete list;
   • search is case-insensitive;
   • max count of items in autocomplete list is 10;
   • users in autocomplete list are sorted by username in alphabetical case-insensitive order.
   • when administrator clicks on item in autocomplete list selected user is added to group.