dialog: Really set ellipsize mode in subtitle and body
Dialog's subtitle or body could not be properly wrapped, while it's ellipsized when the text's width doesn't exceed the container size.
Clutter text has an
ellipsize property, however in dialog's subtitle and body
we have been setting the
ellipsize-mode property to Pango.EllipsizeMode.NONE
that is not present in the underlying GObject.
Fixes #922 (closed)