Test child exclusively breastfed

It certainly could have `num_months=6`, but it defaults to all forms until the end of the report datespan, so basically this will look at all `CHILDREN_FORMS` filled out until the end of month 6 anyways, so I decided to just leave that out.  Happy to stick it in if you prefer to be more explicit, though.

> If vhnd did happen, then it is not met

So does this mean that if they don't have 6 forms with this condition met, we should check and verify that there was no vhnd held and that's the reason they missed one?