Coloring code for CIFTI volume slice viewing was incorrectly setting the alpha...

Coloring code for CIFTI volume slice viewing was incorrectly setting the alpha value.  The RGBA colors are unsigned bytes but the alpha value was treated as a float.   It has been corrected to assign the byte alpha value to the voxel and not multiply the alpha by 255 (incorrectly converting float to byte).  This resulted in a numerical overflow and and incorrect alpha value.