Fixed bug in ThingRegistryImpl (wrong listener was notified when thing was removed).

Signed-off-by: Dennis Nobel <d.nobel@external.telekom.de>
Merge pull request #58 from qivicon/thingregistry-fix

Fixed bug in ThingRegistryImpl
Returning copy of original list in several classes.

Signed-off-by: Dennis Nobel <d.nobel@external.telekom.de>