Changed Graphics Methods

- Added : method Rotate with different interpretation. Hope that this
finally solved the problem of not properly resized image after rotation
(last version -> cropped image)
- Added : method nextOp resolves more operations in row on image.
ShowImage is appointed to DestImage.
- Changed : usability of variables destImage, showImage. ShowImage has
final content. After method nextOp() is showImage appointed to destImage
and we can use another operation that will make new instance of final
showImage.
- Added : method radToAngle(double) that will return angle as double
equivalent to radians that are pushed out as parameter.
- Added : comments to some methods inside class ImageOperation
- Changed : here mentioned conception is used in other method as
betteresize etc.
ToDo : Change method rescale to has parameters that are set by method
changeContrast etc -> try to find out if it's possible to get those
parameters from RescaleOp.