Deployments API Improvementes

[HknLof]

When using our deployments API following points for improvement occured:

• [x] Do not return Kubernetes resources in the API but work with the Deployment spec.
• [x] Align the Deployment spec with the other resources, e.g., Stream, or Pipeline.
• [x] Provide feedback when submitting a deployment to Kubernetes fails. In some cases, no feedback but an uuid is returned by the API, falsely suggesting that no error occured.
• [x] Filter Get methods to only return pipeline-deployments. Can be filtered by labels
• [x] Add Python-Runner as sidecar container
• [x] Change pipeline default image to newly pushed image

[HknLof]

Tests are left, apart from that, this is done!