0031504: Data Exchange - Wrong output of progress indicator when writing to stl

0031504: Data Exchange - Wrong output of progress indicator when writing to stl

Added new condition for first indicated element at Draw_ProgressIndicator::Show(),
because it’s more logical that at start progress starts at 0
Changed usage of Next() to Next(step) for increment progress to IND_THRESHOLD in RWStl::writeASCII() and RWStl::writeBinary()
Changed condition for continuation of writing and add interrupt to this function
Added possibility to use Progress indicator in writestl
Changed paremeter in constructor Message_ProgressSentry aPS() IND_THRESHOLD to 1
Changed test