Add option to partially update data on local server feature

[DerAndereAndi]

Right now a local server feature only allows setting the complete data set. This will then always trigger a full notify to all remote client features, even though data they are interested in might not have been changed.

To improve this, an UpdateData feature should be introduced, that supports deletion of (partial) data and updating new data. This should then trigger a partial notify for this data only and be merged locally.

This should be possible to be implemented with the same/similar way a remote partial update is processed.

I think if it is fine, to expose an update the requires the API user to actively think about deletions, partial updates in the way SPINE does it. Then the stack wouldn't have to do any magic but the API user has to really know what they are doing.

[DerAndereAndi]

This is implemented via #20