added InterpolateStrategy interface
added LinearInterpolation
added default constructor
added isNan(double)

Signed-off-by: Marcel Schwittlick <marzzzel@gmail.com>
refactored functions

Signed-off-by: Marcel Schwittlick <marzzzel@gmail.com>
added namespace

Signed-off-by: Marcel Schwittlick <marzzzel@gmail.com>