Merge "testing" periods into one

Accept a "weeks" parameter that indicates when individuals want to move from testing to enforce periods. This will merge our current system of having two "testing" periods-- one invisible and one visible (on the policy list), and ask people submitting via the form to commit to an "enforce" period in a finite period of time.

I'm in the process of splitting this up into PRs. Generally, I think this will be:

- [x] Small Validator refactor (Use go-y config object)
- [ ] DB => DomainStore refactor (Stop using DB interface for everything-- break this chunk out)
- [x] Accept "weeks" variable in `queue/` API
^ These have no dependencies and can each be merged individually! The final PR, however, depends on all three being merged:
- [ ] Alter Queued Validator to promote/fail domains automagically