More column for the output of stat

[ldevillez]

Is your feature request related to a problem? Please describe.
It could be use full to get more infos in the tree output:

• Mass of the component

• Total mass of the component in its direct assembly

• Total mass of the component in the full depth

• if an assembly has 2 times a sub-assembly and this sub-assembly has 2 times a component, we should see:

• Mass of the compoment

• 2 * Mass of the component

• 4 * Mass of the component

Also an Idea in #12 is to add a column with the conf.