most importantly, the pressure update by the linear system of
equations is now considered to be mainly a hint for the linear
solver. the peaceman well class thus always calculates the bottom hole
pressure which exactly corresponds to a given state of the grid before
each iteration. (this is because calculating the BHP is really fast
compared to requireing more non-linear iterations.)
also, the well residual is now used for all calculations and has been
simplified a bit.
finally, the wells class now provides more methods which allow to
query its internal state (i.e., surface and reservoir rates, BHP/THP,
rate targets, etc.)