Implement the feature described in https://jira.magnolia-cms.com/browse/MAGNOLIA-6664, but definable in JCR configuration.

Summarized: When creating a definition in JCR - it is possible to use an "inherits" feature such that the current definition starts with all properties of the inherited definition, but can then override those values with new ones.

The "inherits" feature is similar to "extends", except that with "inherits" you refer to a definition in the registry (no matter what source created the definition), and that it is only possible to inherit a complete definition. (not a sub part of a definition.)