Added some functionalities to DirSearcher to load the images to cv::Mat

Revised the solution to the problem to use QMap<QString, QString> to get
the original along with all the copies found of it.

Got the comparator to do the copy-checking instead of the window class,
seems to fit more to it.
Merge branch 'master' of https://github.com/DatCorno/Image-Duplicate-Finder