Introduce QtTr class

This class is populated with translations for Qt itself.
FileSystemSortFilterProxyModel: use filePath() instead of fileName()

fileName() returns the volume name of a drive entry. So the order of
drive entries can be misordered.
Update Korean translation
QtTr: query the translation for 'Type' with disambiguation

Korean translation does not work without this.
KFileWizard: add version() to retrive a version string
translation: update Korean translation