Package-level declarations

Compares the wall-clock time taken to solve the N-Queens counting problem with it.unibo.tuprolog.solve.concurrent.ConcurrentSolverFactory (backed by it.unibo.tuprolog.solve.concurrent.ConcurrentSolver, which explores alternative choice points on separate threads/coroutines) against the same query solved with it.unibo.tuprolog.solve.classic.ClassicSolverFactory (a single-threaded, depth-first resolution engine).

Entry point running the N-Queens benchmark first with the concurrent solver, then with the classic solver, printing the elapsed time of each run to standard output so the two engines can be compared directly for the same theory and query.