Add __all__ to color package
Add __all__ to exposure package
Explicitly import color functions
Add __all__ to data package
Add __all__ to draw package
Add __all__ to feature package
Add __all__ to filter package
Add __all__ to rank filter package
Add __all__ to graph package
Add __all__ to measure package
Add __all__ to morphology package
Add __all__ to segmentation package
Add __all__ to transform package
Add __all__ to util package
Fix selem test cases
Fix hough transform test cases