Remove UTF-8 BOM from source files

[lassoan]

These source files start with UTF-8 BOM, which causes build failure on Korean computers:

CTK\Libs\DICOM\Core\ctkDICOMRetrieve.cpp
CTK\Libs\DICOM\Widgets\ctkDICOMJobListWidget.h CTK\Libs\DICOM\Widgets\ctkDICOMPatientItemWidget.h CTK\Libs\DICOM\Widgets\ctkDICOMSeriesItemWidget.h CTK\Libs\DICOM\Widgets\ctkDICOMStudyItemWidget.h CTK\Libs\DICOM\Widgets\ctkDICOMVisualBrowserWidget.h

The build scripts should be improved to not be sensitive to the presence of a UTF-8 BOM, but for consistency, we should not just start using BOM for some source files. For now, the easiest is to keep using ASCII in all CTK source files. If there is a good reason to change this in the future then it should be changed for all source files.

[Punzo]

Done in #1215