Stats for magnifying glass

Fixes #15.

We already keep stats for magnifier calls (# sat/unsat calls, time spent). This commit exposes/prints these statistics in the summary at the end of running the algorithm.

There is also a change to magnifier so it returns the number of solutions it found at that Pareto point (which will always be at least 1). This is used so the algorithm that called magnifyingGlass can log how many solutions were at the Pareto point, and the current time.

Finally, this commit also adds some logging back to IGIA.

Reviewers: @AtulanZaman @cpkleynhans @joseph2625