Various bugfixes for cropping & rotation handling

[stefan-it]

Hi,

this PR fixes various cropping & rotation handling bugs:

• Calculation of image boundary exceeding was done wrong: when e.g. image is rotated 90 or 270 degrees, the image dimensions switch. Refactored image boundary exceeding check was added to work with rotation at 90 and 270 degrees.
• In some cases, negative coordinates for region width and height could occur
• Also in some cases, region width and height could be less than the user-defined values. This was due to the fact, that Math.min was used. A new function was added that checks, if the calculates value for region width and height is >= the user-defined value.
• An extensive unit test was added, that uses a sliding window approach: a rectangle slides over an input image and rotation operations (90, 180 and 270 degress) are performed. The returned image is checked to match the user-defined dimensions. This check shows that no regression bugs were introduced with the new rotation handling and the library is now more robust when using rotation operations.