This commit adds a level of indirection to the current per-group
summary quantities that is directly assigned by the simulator. In
particular, introduce a new structure named
GroupData
that contains a 'GroupConstraints' object and make the per-group
values into 'map<string, GroupData>' rather than the current
'map<string, GroupConstraints>'. This is in preparation of adding
support for reporting group-level production/injection guiderates
(Gx[IP]GR) to the summary file.
Update tests and APIs accordingly.
68b4f38464