Let XBoard propose name of tourney file

Let XBoard propose name of tourney file

Add an option -defaultTourneyName to configure the name that will be
proposed in the Tournament Options dialog's tournament-file field. The
option can contain %y, %M, %d, %h, %m, %s for year, month, day, hour,
mintes, seconds of the curret time in %02d format, or %Y for the year in
%04d format. Any tournament -file name is ignored when no participants
are given. Participants without a tourney file remains an error.