Export and import of models
- Reused/recursive elements
- Additional roots
(from redmine: issue id 826, created on 2018-01-22tgradl)
- Relations:
- relates #839
- relates #858
- relates #788
- relates #832
- relates #857
- relates #863
- relates #860
(from redmine: issue id 826, created on 2018-01-22tgradl)