Implemented the ability to make groups from a list of lists of persons.

social-net-functions:
-Persons who already exist can be put in a list of lists, where each sublist is a group.  Their 'groups and 'talks-to properties will be updated to reflect the new group's creation.
-A lot of helper functions got added; code documentation should be sufficient though.

multi-group-model:
-trivial changes in comments

make-groups-model:
-makes 10 people and a pundit who talks to everyone.  The 10 get put into groups, then the pundit gets 5 ticks to talk.  After that, the pundit is silenced.