Provide easy to use "frontend" APIs

In order to integrate the catalogue with further GXFS components, there is a need for easy to use APIs that can easily be integrated into a UI. This should implement

• simple commands such as /upload or /store to easily upload any kind of schema (ontologies, SHACL shapes, …) or Self-Descriptions without worrying about its type (as long as it is valid) – it is possible for the Catalogue to auto-detect the type,
• and a /find function to easily query for simple parameters to find the fitting Self-Descriptions. This should be usable without extended openCypher knowledge (e.g. "find all SDs of a certain type").