Removal of single object editing in myAX fronted

As announced via our deprecation warnings, we removed the data editing interface for single data objects in the frontend.

This feature is not relevant to the current use cases anymore since it could not be used on JSON-based or nummer5-provisioned data and caused a lot coding-side overhead.

Adding single JSON based objects (e.g. for testing purposes or creating example things) is available in the training wizard directly: