In current version all dimensions can be used or
not
People who want to enter length+width+heigth, yuo can do
so. In such cases, volume is autocalulcated.
People who don't want to enter immediatly a volume, and
don't want to have volume calculated, can also do this. All
user have to do is to enter a volume and not length, nor with,
nor heigth.
Well, may be there is some problem with this rule, but this
is what we how we want to work.
Goal is that every body able to use the dimension he
want/need to use and only this one.