Correct Land Values Model

After the Land Price Model runs at least for 2 years, the production code invokes every year a model called CorrectLandValue. This model makes a correction of the land value to avoid its declination with development type change.

Its run() method determines those members of dataset whose development type changed and at the same time have lower total land value when comparing to previous simulated year. Values of the attributes ``residential_land_value'' and ``nonresidential_land_value'' of these members are replaced by values of the same attributes from previous year. The method returns an index of the modified dataset members.