[Epic] Have an educational and introductionary sample project

[nkoester]

Goal of this Epic is to bring the samples to a functional and educational state so that developers can easily experiment and gain experience with modelix.

Things to do for this:

• reorganization: rest-api-json-bulk #11
• Quarkus model server REST API #13
• Single page application using openapi spec #14
• Add modelix model-server cloud plugin to the project #18
• Folder/README refinement & legacy component cleanup #19
• Generate models for ktor example #20
• Specify a distinct base package for the model-server example #21
• Feature/document running model server example #22
• Add an example for modifications #23
• Add an example for update notifications #24
• Automate sample project, especially model-server setup #25
• Add gradle task to start temporary model-server #26
• Fix server in OpenAPI spec #27
• Update notifications in the model-server example #28
• Frontend with websocket-based updates #32
• Use api-gen v2 in samples #36