change XDG_APPS_DIR -> XDG_APPS_INSTALL_DIR, XDG_DIRECTORY_DIR->XDG_DIRECTORY_INSTALL_DIR, DBUS_INTERFACES_DIR->DBUS_INTERFACES_INSTALL_ DIR, DBUS_SERVICES_DIR->DBUS_SERVICES_INSTALL_DIR to have same naming convention as discussed with Alex.

svn path=/trunk/KDE/kdebase/workspace/; revision=691218