#2 Add Team desirability criteria

[N Napier]

Another important criteria to consider when assigning teams: are there certain students that would strongly prefer to work together or strongly prefer *not* to work together? We have used the term "team desirability" to refer to these student preferences. Need to
(a) find a suitable format for capturing these preferences
(b) change the GroupUpApp to read in team desirability preferences
(c) change the group processing to consider these team desirability preferences