Separate released models and snapshot/draft models

[aedelmann]

When models are published with a version format, e.g. 1.0.0-SNAPSHOT or 1.0.0-DRAFT, these are stored in the snapshot workspace automatically. Snapshot models can be overridden by the user multiple times until it reaches "Release" quality. The user can then change the model version to 1.0.0 indicating the release state. These models go into the release workspace.