Use shared widgets from libkexiv2 1.1.0 (KDE 4.5), already used in digiKam core :

- Remove topicset.iptc-subjectcode.xml                                                                      DONE
- Port IPTCSubject and XMPSubject classes to KExiv2::SubjectWidget (see Digikam::SubjectEdit for details).  DONE
- Use KExiv2::AltLangStrEdit instead locale class.
