[TESTING] Some more benchmarks

[bchevalier]

• More infeasible problems to make sure the phase 1 of the simplex is correctly tested
• Simplified the quadratic relaxations. They now correspond to the quadratic relaxations of the new added infeasible problems 1, 2 and 3.
• Added Stigler diet's problem, see: https://developers.google.com/optimization/lp/glop

A few words about the link. It corresponds to the introduction page for google's linear solver, namely Glop. It is mentioned at the bottom of the page that it takes less than 300ms for Glop to solve Stigler diet's problem. jsLPSolver takes less than 1.5ms to solve it on my machine. Either they made a typo or jsLPSolver is really fast or Glop is really slow.