[Task] Functionality to import and export namespace packages

[atextor]

Is your task related to a problem? Please describe.
ADR-0009 specifies the layout of so-called namespaces packages, zip files that contain an Aspect Model namespace directory structure and Aspect Model .ttl files.
A samm-cli command is required to create and read these files. This includes at least the following actions:

• Create a namespace package from an input (URN or file) and its transitive dependencies, or from a given set of namespaces and/or aspect model files.
• Import ("extract") a namespace package into a models root directory in the local file system in way that makes sense, with configurable boundary conditions (e.g., "overwrite all", "import only newer versions", "show differences",...)
• A shortcut that transparently combines the two points above in order to sync the state of one model source to another. "Transparently" here means that a user does not see or needs to interact with the intermediary .zip file. The main use case here is "import the latest state from GitHub repository X to local workspace directory Y".

Describe the solution you'd like
For all functionality there needs to be a Java API (so that this feature can be used from the Aspect Model Editor backend) and a corresponding samm-cli command.