[REFACTOR] moved LinkListener class


This an UI (SWT) util class not a generic util class that can be used
without a Widget Toolkit.

Change-Id: I844244aa2d15243031206c7b7b9755a41a31817c
Reviewed-on: http://saros-build.imp.fu-berlin.de/gerrit/1270
Reviewed-by: Stefan Rossbach <srossbach@arcor.de>
Tested-by: Jenkins CI