Refactor Softcopy Presentation State constructors

[hackermd]

This PR introduces the following changes based on discussion on #139:

• Use setter functions to add attributes of modules to instances of Softcopy Presentation State classes instead of deriving the classes from a common base class. This will allow implementation of additional classes (e.g., Advanced Blending Softcopy Presentation State), which contain different modules.
• Remove copy_modality_lut and copy_voi_lut parameters from constructor of GrayscaleSoftcopyPresentationState and friends and instead always copy attributes of Modality LUT and VOI LUT modules from referenced source images by default. In almost all cases, this is probably the desired behavior. In case a developers really wants to override that behavior and not apply a Modality LUT or VOI LUT, a custom Modality LUT or VOI LUT can be provided via the modality_lut or softcopy_voi_lut, respectively, to describe an identity function.
• Fix color management using ICC profiles. Similar to the logic of dealing with Modality LUT and VOI LUT for grayscale images in GrayscaleSoftcopyPresentationState, an ICC Profile from one of the referenced color images will be used by default for ColorSoftcopyPresentationState if no ICC Profile is provided via the icc_profile parameter. For PseudoColorSoftcopyPresentationState, a default ICC Profile for the sRGB color space will be included if none is provided by the developer via the icc_profile parameter.

[CPBridge]

A note that we should update the explanation of the softcopy_voi_luts and modality_lut in the various SOPClass docstrings to make sure that it's clear that they will be copied from the referenced images if none are provided.

[CPBridge]

@hackermd it seems you have forgotten to add a test image called sm_image_grayscale.dcm, so tests are failing for me