/// \brief Returns the 'read length' of the current Dicom Header Entry
/// \warning this value is the one stored in the Dicom Header but not
/// mandatoryly the one thats's used (in case on SQ, or delimiters,
/// the usable length is set to zero)
/// \brief Returns the 'read length' of the current Dicom Header Entry
/// \warning this value is the one stored in the Dicom Header but not
/// mandatoryly the one thats's used (in case on SQ, or delimiters,
/// the usable length is set to zero)