ActiveSetQuadratic with weights and atoms passed directly

[matbesancon]

The constructor of ActiveSetQuadratic is a bit of a hassle, there should be a way to separate the preparation of weights, atoms, and x, and all the rest of the quantities tracked down. Something like reset_quadratic_terms!

[sebastiendesignolle]

Absolutely true, will fix this! Btw, I never really understood the necessity of having two constructors for ActiveSet, namely, one with and one without types. I'd be tempted to have one call the other, anything speaking against this?