Compress: Detect binary images and encode with a binary image encoding algorithm

[gunnsth]

Images with only 2 values (min/max) are suitable for encoding with CCITTFaxDecode and JBIG2 (when encoding support is ready).

Add a flag BinaryImageOptimization = true by default which looks at the image values and detects whether it is suitable for encoding with CCITTFaxDecode. Note that this is slightly different from #428 as this involves looking at the values (color histogram), for example a BitPerComponent = 8 using only color values 0/255 would be suitable for encoding as a binary image.

It might also make sense to define some threshold so that the number of pixels outside the min/max bins could be defined so that a certain percentage of pixels could fall outside and would be interpolated to the closest bin. For example if 99% of pixels fall into 0, 255 and then there are some pixels with values 1,5,9,230, 150, 250, those would be interpolated to the closest value 0,0,0,255,255,255 so that there are only 2 values prior to feeding to the CCITTFaxDecode algorithm. The threshold should be defined as BinaryImageOptimizationThreshold = 0.99 (float64).