Adds the following features to support rulesets:

1. A rulesets field in the organization module to make organization wide rulesets
2. A rulesets field in the repository modules to make rulesets at the repository level
3. A few variables to add predefined rulesets to an organization that protect the default branch of all repos in the organization:
   1. A ruleset that prevents deletion, force pushes, and requires a PR to merge commits into the branch
   2. A ruleset that requires a minimum number of approvals from reviewers that aren't the code submitter
   3. A ruleset to dismiss stale reviews
   4. A ruleset that requires commits to have verified signatures