Deprecate yamlapi.py

I suggest to deprecate and remove the module yamlapi.py in caosdb/. The functionality should be covered by caosdb-advanced-user-tools/models/data_model.py, so this module might lead to more confusion than enhancement. Furthermore it is not really documented.

Suggestion:

• Check existing code in pylib and caosdb-advanced-tools for references to that module and open issues for all necessary changes.
• Add deprecation warnings to all functions (https://docs.python.org/3/library/warnings.html)
• Add module to CHANGELOG (under "deprecated")