Contentbox Modules should have Forgebox Entries

In order to become truly modular and to de-couple the dependencies, each module in the Contentbox namespace should have a separate Forgebox entry, to allow for truly modular deployments.

This would allow the omission of the installer/dsncreator on container-based deployments with existing configurations, as well as separate deployments for the administration module. The `contentbox` module should include all of these as dependencies by default, but a root `box.json` could be configured to only contain the modules necessary for that build/deployment.