Correct initializer list order found by cuvs

[robertmaynard]

Align our constuctor order to match what C++ spec says will occur:

Then, non-static data members are initialized in the order they were declared in the class definition (again regardless of the order of the mem-initializers).

Otherwise consumer of raft will get warnings when building with -Wall -Wextra and using the index type.

[cjnolet]

/merge