Changed selection interface

The qicons have been replaced by QString. The path to the icon has to be given now
This avoids the problem of qpixmap creation in the selection plugins, when no gui is present
Added deprecation warning, to informa about deprecated plugin interface usage

git-svn-id: http://www.openflipper.org/svnrepo/OpenFlipper/branches/Free@15791 383ad7c9-94d9-4d36-a494-682f7c89f535