This commit adds a new member function
WellProdIndexCalculator::reInit(const Well& well)
which reinitializes the internal arrays in the same way as the
constructor. This is needed to ensure that the PI calculation
device is synchronised in the case of CTF rescaling-e.g., as a
result of WELPI.
Switches between using the logarithmic and unit scaling factor based
on whether or not the well has an explicit, positive drainage radius
(WELSPECS item 7). Does presently not include the D factor.
Add a set of unit tests to exercise the facility.
