TSAC-2637

Floor layout: Seam modification has changed so that all zero seam gap dimensions are now shown when any of the seam gaps has a value other than zero.
Note that in this situation the first and last zero dimensions are also shown, and if you change either of them to some other value than zero, the setting No gap at first and last on the General tab is changed to allow a non-zero gap at the first and last seam.