feat(ColorMaps): Add grayscale sigmoid colormap based on DICOM standard

Add a non-linear sigmoid grayscale colormap as an alternative to
linear grayscale.
This mapping is described in the DICOM standard in section
C.11.2.1.3.1 SIGMOID Function and equation C.11-1.
We use a normalized window_width of [-1, 1]
and window_center = 0.
The colormap is generated using a 16-point sampling of this function.

Author: jadh4v

Sources/Rendering/Core/ColorTransferFunction/ColorMaps.json

@@ -529,6 +529,78 @@
       "NanColor" : [ 1, 0, 0 ],
       "RGBPoints" : [ 0, 0, 0, 0, 1, 1, 1, 1 ]
    },
+   {
+      "ColorSpace" : "RGB",
+      "Name" : "Grayscale-DICOM-sigmoid",
+      "Notes": "This is a 16 point sample of a sigmoid grayscale colormap described in the DICOM standard. See equation C.11-1 in section C.11.2",
+      "NanColor" : [ 1, 0, 0 ],
+      "RGBPoints" : [
+         -1,
+         0.01798620996209156,
+         0.01798620996209156,
+         0.01798620996209156,
+         -0.8666666666666667,
+         0.030275691986950463,
+         0.030275691986950463,
+         0.030275691986950463,
+         -0.7333333333333334,
+         0.05053016223541345,
+         0.05053016223541345,
+         0.05053016223541345,
+         -0.6,
+         0.08317269649392238,
+         0.08317269649392238,
+         0.08317269649392238,
+         -0.4666666666666667,
+         0.13392788832407365,
+         0.13392788832407365,
+         0.13392788832407365,
+         -0.33333333333333337,
+         0.2086085273260449,
+         0.2086085273260449,
+         0.2086085273260449,
+         -0.19999999999999996,
+         0.31002551887238755,
+         0.31002551887238755,
+         0.31002551887238755,
+         -0.06666666666666665,
+         0.4337256058045608,
+         0.4337256058045608,
+         0.4337256058045608,
+         0.06666666666666665,
+         0.5662743941954392,
+         0.5662743941954392,
+         0.5662743941954392,
+         0.19999999999999996,
+         0.6899744811276125,
+         0.6899744811276125,
+         0.6899744811276125,
+         0.33333333333333326,
+         0.791391472673955,
+         0.791391472673955,
+         0.791391472673955,
+         0.46666666666666656,
+         0.8660721116759263,
+         0.8660721116759263,
+         0.8660721116759263,
+         0.6000000000000001,
+         0.9168273035060777,
+         0.9168273035060777,
+         0.9168273035060777,
+         0.7333333333333334,
+         0.9494698377645865,
+         0.9494698377645865,
+         0.9494698377645865,
+         0.8666666666666667,
+         0.9697243080130495,
+         0.9697243080130495,
+         0.9697243080130495,
+         1,
+         0.9820137900379085,
+         0.9820137900379085,
+         0.9820137900379085
+      ]
+   },
    {
       "ColorSpace" : "RGB",
       "Name" : "BkRd",