* src/gdcmParser.[cxx|h] and gdcmHeader.[cxx.h]: gdcmHeader::Write split

 * src/gdcmParser.[cxx|h] and gdcmHeader.[cxx.h]: gdcmHeader::Write split
       in WriteEntryTagVRLength and WriteEntryValue. Those methods were
       moved to base class gdcmParser and only the specialisation is kept
       in gdcmHeader.
     * src/gdcmParser.[cxx|h]: ReplaceOrCreateByNumber(char*, guint16, guint16)
       trashed out (because ReplaceOrCreateByNumber(string, guint16, guint16)
       allready does the job.
     * src/gdcmDicomDir.[cxx|h]: WriteDicomDirEntries renamed to WriteEntries
       (to be consistent with gdcmParser::WriteEntries).