KernelLookup should not be inherited from DataLookup2D

[Peter]

daughter of ticket:287

needs ticket:316, ticket:315, ticket:314 and ticket:313

New description:

Two things to do. Remove inheritance and start using SmartPtr? class. In DataLookup2D we need a SmartPtr<utility::Matrix>, and in KernelLookup a SmartPtr<Kernel>. MatrixLookupWeighted will have an additional SmartPtr<utility::Matrix> for storing its weights.

Old description:

I suggest that we create a common interface class (named e.g. AbstractMatrixLookup) for MatrixLookup and MatrixLookupWeighted. AbstractMatrixLookup should in turn be inherited from DataLookup2D. This implies the three concrete classes MatrixLookup, MatrixLookupWeighted and KernelLookup are not equal sister classes, but MatrixLookup and MatrixLookupWeighted are tighter coupled together.

The reason behind this suggestion is that there are several places in which a DataLookup2D& is passed, but a KernelLookup is not expected. For example see member s of Kernel, NCC, and NBC.

[Peter]

(In [1126]) working on ticket:234