Task 4a - Create Island Grouping Schema in DB

[nickrsan]

• [ ] Need to add a pre-save trigger to make sure that 1. regions in group are in the same model area and 2. That a region isn't in multiple groups in the same group set.
• [ ] Need a test that adds modifications for a group and another run with modifications for all the regions in the group that match and confirm they're the same results
• [ ] Need a test that adds modifications for a group, as well as overrides for specific regions, along with another that matches those at individual region level and confirm those match as well.