Implement Schema Decoration

[mehalter]

Implement a database Schema decoration on a cospan of finite sets, define necessary category theory morphisms to solve pushout, dpo, etc.

Show that an instance of the category creates a database instance that can hold valid data that would be inputted into the model.

[jpfairbanks]

Per conversation today:

1. Schemas associated with each FinSetCospan have a table for each state
2. The rows of that table are observations of the entities (tokens) that inhabit that state
3. The columns are (primary key, entity id, timestamp, fk1, fk2 ...)
4. Foreign keys exist if there is "transitioned to" relation between two observations
5. A join on this FK returns "the set of state transitions"