Follow-up from "Add "OrthogonalRecursiveBisection""

The following discussion from !95 (merged) should be addressed:

@frey_m started a discussion:

Why don't you use the members?

In Index.h the types are as follows: int first_m; size_t length_m; Therefore the casting in Index.hpp for the 3 split functions is required to compile.. need to change member variables types in order to remove this casting.