Add a "progress" argument to the callback function.

[EliteMasterEric]

Since the simulated annealing temperature has a known start and end value (from 100 * distance from point 0 to point 1 to 1e-6), progress can be represented by the size of the current temperature.

Not sure of the best way to calculate the percentage from that, but the result can be passed to the callback function to be used for progress bars.