* Migrate PR pipeline definition into main repo
* Move credentials from LastPass to CredHub
* Reference docker images in tasks to allow use of `fly execute`
* Make use of var templating everywhere to make `fly execute` easier
still
* Move pipelines to `app-broker` Concourse team
* Separate CI management scripts from Concourse task scripts
* Template git-repo-staging user data
* .envrc
* Fix `InMemoryServiceInstanceBindingStateRepositoryTest` failure when
the time rolls over into a new minute during test execution :D
closes#381
(cherry picked from commit 7ca3239ba6)
