text: Title: Docstring of `color.hsv_value` is incomplete
  Body: ## Description
  
  `color.hsv_value` is incomplete:
  
  https://github.com/scikit-image/scikit-image/blob/09577eddf2ce0376b25b96291599af313adb1c2d/skimage/color/adapt_rgb.py#L48-L59
  
  `args` and `kwargs` should be documented as well as the return value. It could also be made clearer that `image` expects an RGB(A) image.