Idea: implement cycle cutting

[pvdz]

The idea of a cycle cut is to find secluded groups of variables such that the constraints that use them do not use variables outside that group. Smaller groups have smaller search spaces which may lead to considerable improvement in solving time. These disjointed groups can be solved independently from each other, in parallel even, as a solution to on group will not affect the other group(s).

I've already tried to implement this once and my conclusion at the time was that finding these cycles is rather expensive. To make matters worse most configurations had little to no cycles in the first place; every var was somehow tied into every other var. And in the cases where something was found, the overhead outweighed any potential gains.

We should still revisit this as I'm not convinced that the approach is useless.