Add mutable matrix structure builders

[EjenY-Poltavchiny]

I'm working with "series" (kmath - stat) package and my task is to implement DTW algorithm. To implement this algorithm I need to dynamicly change special matrix. But I faced with the problem, that MatrixBuilder is immutable structure. As a result, I was sent here to create issue.

[SPC-code]

Mutable matrix exists (MutableStructure2D). But there are indeed no suitable builders for this kind of structure.