Enable switching between families. about lineage

[alexsb]

Revising this: we want to be able to switch between different families which are all in the same dataset. In addition, we want a small view that lists the families and important attributes about them, such as the number of nodes and the number of "cases".

[ngehlenborg]

Should this be part of the attribute browser? It might be appropriate to place the family selection at the top in a separate section.

[alexsb]

Yes, spatially that's the plan. I think it should be it's own view/class though.

[cnobre]

Done!