FE/Qt: language string updates.
FE/Qt4-OSX: fix the translation of the application menu
FE/Qt4-NLS: Merged Serbian, Bulgarian, Italian, Czech, Slovak, Spanish & Japanese.
FE/Qt4-NLS: updated qt_* translation files to 4.4.3
renamed VirtualBox4 to VirtualBox
purge the obsolete Qt3 GUI
FE/Qt: NLS: Updated Greek, Slovak (Qt3), Catalan, Romanian, Czech and Chinese translations.
FE/Qt: Added Slovak translation.
FE/Qt: Corrected syntax of some qt_xx translations.
FE/Qt: Added Qt translation sources from the Qt distribution; created untranslated sources for existing languages; added code to load Qt translations on language change.