Add "type" field to InstitutionGroup

type can be:

• K12 k12
• Public Library publiclib
• Higher Education highered
• Default default

This value can be set in the seeds file (see this method or @bmb for the mapping), but the AMPALS type may need to be set via another migration for the dev/staging environments.

With this field, we can determine how many and what type of SpotlightConfigurations should be created for Institution records.