Data conversion in VMI12: compute area weights of forest stands

[Sorvalampi]

Data conversion in VMI12: compute area weights of forest stands.

In the case of VMI12, there are two area variables in data structure: actual area and area weight for the growing stock. Area weight for the growing stock should be calculated:

area weight for the growing stock = actual area *(osuus9m/10)

[Sorvalampi]

This is closely related to #37 (implement these both in the same version).