refs https://github.com/TryGhost/Toolbox/issues/363
- this middleware is standalone and I suspect we're going to be touching
it further when we work on Ghost's caching in the near future
refs https://github.com/TryGhost/Admin/pull/2252
closes https://github.com/TryGhost/Team/issues/1182
- Admin now copies it's build output to a single env-specific directory rather than splitting html and assets
- `core/built/admin/{development|production}/*`
- updated the admin app's `serveStatic` definition for assets and controller's html serving to reflect the new asset paths
refs https://github.com/TryGhost/Toolbox/issues/354
- this commit turns the Ghost repo into a monorepo so we can bring our
internal packages back in, which makes life easier when working on
Ghost
