C++ code should not pop up message boxes

[hmeine]

At least two locations try to pop up Windows message boxes as some kind of error handling:

• Community/General/Sources/ML/MLDicomSurfaceSegmentation/tools/dicom/dicomSSODatasetParser.cpp
• UMD/METK/Sources/Inventor/UMDSoMeasurement/UMDSoMaximumExtension.cpp

It is probably better to handle errors differently, and not to mix business logic with GUI code. In particular, calling code cannot "see" the errors this way, and end users faced with these messages probably cannot do anything about them. (Developers, on the other hand, should be fine with exceptions and/or log messages.)

Also note the phrase "Windows message boxes". UMDSoMaximumExtension.cpp does compile on other platforms (logging instead), while MLDicomSurfaceSegmentation currently fails due to the missing API.