Create an abstract class for interpolation

[lachlangrose]

I want to be able to use different interpolation algorithms for interpolating the orientation cosines and thicknesses - in theory using a discrete approach should be a lot better when we have a lot of data...

So can we create a base interpolation class that is used for the interpolation throughout map2loop and then create child classes that manage how each specific interpolator needs to be setup? Basically the same thing I have done with LoopStructural using the GeologicalInterpolator and the different daughter classes for discrete inteprolation approaches?