Conflict resolution

As stated before, a conflict is a satisfied incompatibility. We may detect such conflict while generating new derivations in the unit propagation loop. Given a satisfied incompatibility, conflict resolution aims at finding the root cause of the conflict and backtracking the partial solution just before the decision at its origin.

TODO: explain how finding the earliest satisfier fits into this.

TODO: explain that prior cause is just the previously explained rule of resolution on two incompatibilities, the current one, and the one being the cause of the earliest satisfier.