Adds VecN class to represent vectors of real numbers.
Adds a custom graph Edge, a generator for MDGP instances, removes VecN and adds Breeze for linear algebra.

The custom edge was added because the scalax package doesn't support double weights.

Added a generator for moreWu mdgp instances, still need to define a particular type of graph as a problem instance.

Decided to save myself some headaches and added the Breeze linear algebra library, instead of making my own vectors (and other stuff).