refs https://github.com/TryGhost/Toolbox/issues/364
- This is a groundwork which moves the "cache" property in settings cache to be injectable parameter, so we can swap it out with different implementations.
- The module will be broken downn into two concepts - an injectable cache and a cache manager (the update system)
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