* Fixed PdfColorspaceSpecialIndexed.ImageToRGB() Fixes https://github.com/unidoc/unipdf/issues/258
* Fixed indexed colorspace bounds checking.
* Being super cautious to prevent a divide by zero error. I don't think the base cs can have <1 cpts.
* Updated image hash in extract_images_test.go to match new indexed colorspace code.
* add testfile from unipdf#258
* Take decode arrays into account when processing grayscale images
* Adapt image extraction test case hashes
* Minor refactoring in the ColorAt image method
* Always return vanilla data from the jbig2 decoder
* Add ColorAt method for images
* Avoid resample on image to Go image conversion
* Avoid resample when converting grayscale image to RGB
* Preserve old behavior of image to Go image conversion
* Add missing case in the ToGoImage method
* Fix grayscale to RGB image conversion
* Improve code documentation
* Fix color extraction for CMYK and 4 bit RGB
* Add test case for the ColorAt image method
* Avoid resampling when converting CMYK image to RGB
* Add notice comment for the GetSamples/SetSamples image methods
