Terminal criteria for solver.

This method is not necessary to be called before the first call to cv.DownhillSolver.minimize, as the default value is sensible.

Algorithm stops when the number of function evaluations done exceeds Termcrit.maxCount, when the function values at the vertices of simplex are within Termcrit.epsilon range or simplex becomes so small that it can enclosed in a box with Termcrit.epsilon sides, whatever comes first.