BToolbar: Allow the toolbar's orientation to be set by its creator.

I already made this patch in Heidi's clone of BToolbar. Adding it here
allows me to drop Heidi's version altogether.

I also relicensed the header file at the permission of Stephan. The .cpp
file still lists him as author and copyright holder.

Signed-off-by: Jessica Hamilton <jessica.l.hamilton@gmail.com>