Add report API to manipulate and create method content

Add a report API to manipulate and create method content.

The API should cover:

Creating and deleting user defined method content (attributes types, model types, symbol types, ...).

Editing standard and user defined method content (e.g. changing the name).

Assign and remove standard and user defined method content to item types (e.g. add or remove attributes / symbols / object to a model type, add or remove connection types to object types, ...).

Create, edit and remove user defined method filters.

This could be limited to attribute types at first because that currently results in the most amount of manual work.