Dublicate entry error message, if a entry exists

Problem/Motivation

If You start a safely import (for example for taxonomy terms) and in the structure_syn_data are existing taxonomy terms, You get an error: Integrity constraint violation: 1062 Duplicate entry, which is correct, because the entry is already there.

It would be much nicer, if the import would skip those existing entries, and import the rest.
What You have to do now is to delete the existing entries in the yml-File by hand and than import the configuration.

A fantastic feature would be, if the exsting entries would be updated and the new entries would be insert. May be with a question before updating the old values.

Greeting
Berthold

btw: i really like this module, great work :-)