Export/import: export should include super-type definitions, import should preserve system attribute values

When type of the entity exported has super-types, the type-def of the super-types are not included in the exported file. This can cause the import to fail, if these types are not present in the instance.

For imported entities, the system attribute values (create-time, modified-type, created-by, modified-by, status) should be preserved as in the exported file (i.e. source system).