ThingHelper#createAndBindItems: items and links will be reused, if they exist already

Signed-off-by: Andre Fuechsel <a.fuechsel@telekom.de>
added author tag and removed one unused imports

Signed-off-by: Andre Fuechsel <a.fuechsel@telekom.de>
Merge pull request #115 from qivicon/reuse-items-and-links

Graceful creation of items and links in ThingHelper