Track constraint checking status in the database

[camargo]

We need to reflect the status of constraint checking the database. This should be similar to how we store simulation and scheduling statuses.

[joswig]

We also need a design for persisting constraint check results. They currently aren't tracked and need to be re-run. If it makes sense we can split that into another issue

[cohansen]

I think we need to do both of these things at the same time, each constraint_run (or whatever this new table is called) record should contain the status of the result, and probably some other properties as well. I'll take a look at the db to see how scheduling and simulation handle this.