0011842: import full related record data

0011842: import full related record data

* allows to import all related record (scalar) fields

side effects:
* setRelations(): use existing relations if only relation id is missing
* makes deleteLinkedRelations public (to be able to
 use it in test case cleanup)
* show relations in CRM lead duplicate conflict panel
* improve plugin failure message

https://forge.tine20.org/view.php?id=11842

Change-Id: Ic9e01d3d5797ff009f5bffbb02ef6f7c34be2cd6
Reviewed-on: http://gerrit.tine20.com/customers/3131
Tested-by: Jenkins CI (http://ci.tine20.com/)
Reviewed-by: Philipp Schüle <p.schuele@metaways.de>