IOManager: added another interpolate procedure that takes as arguments a Date, a DEMObject, the parameter to interpolate, a vector of Coords objects and a vector of doubles. The Coords represent different points in the DEM. The interpolation is only performed for these points and for each point one double value is stored in a vector. 

Furthermore IOManager now has a member variable called interpolater of type Meteo2DInterpolator. A circular inclusion problem has been solved between IOManager and Meteo2DInterpolator.

libinterpol2D bugfix: The SimpleDEMWindInterpolate algorithm had  a small bug in it, it wasn't interpolating values in the last row or last column of the 2D grid.