BfgsMinimizer - ReasonForExit

[MartinCernak]

In the BfgsMinimizer, the reason for exit is always the absolute gradient.

 return new MinimizationWithLineSearchResult(candidate, iterations, ExitCondition.AbsoluteGradient, totalLineSearchSteps, iterationsWithNontrivialLineSearch);

I believe that the reason for termination should be set by checking the conditions of termination.

return new MinimizationWithLineSearchResult(candidate, iterations, currentExitCondition, totalLineSearchSteps, iterationsWithNontrivialLineSearch);

It's not a big deal, but it can help when setting optimization parameters...