Some interface was refined (most notably, the method for returning
Hessian was removed and the method for getting gradient was added as
optional to base Solver::Function class) and basic code for
setters/getters was added. Now is the time for the real work on an
algorithm.
In response to the pull request comments by Vadim Pisarevsky. In
particular, the following was done:
*)cv::reduce use instead of custom code for calculating
per-coordinate sum
*) naming style of private methods is made consisted with overall --
mixed-case style
*) irrelevant create()'s were removed -- I did not know that copyTo()
method itself calls create
