* In order to fix writing of dicom files:

   * In order to fix writing of dicom files:
     - Test/TestWriteSimple.cxx: a simpler example of writing.
     - Test/CMakeLists.txt changed accordingly.
     - src/gdcmDocument.cxx:
       -- The destructor now recursilvely removes potential sequences.
       -- Bug fix in ::IsJPEG2000()
       -- ::ReplaceOrCreateByNumber(std::string, guint16, guint16)
          now handles promotion of gdcmDocEntry to gdcmValEntry in a cleaner
          manner.
       -- ::GetValEntryByNumber(guint16, guint16) now defined (as opposed
          to only declared) and build on top of
          ::GetDocEntryByNumber(guint16, guint16).
       -- ::SetEntryByNumber() now uses GetValEntryByNumber(group, element)
     - src/gdcmElementSet.[h|cxx]: added ::RemoveEntry(gdcmDocEntry *)
       for usage in destructor and treatement of promotion in
       ::ReplaceOrCreateByNumber().
     - src/gdcmSQItem.cxx: destructor should better handle his job.
      Test/TestWriteSimple now runs (or at least it DOES something).
    * We can now start hutting memory links. A good starting point is:
      valgrind -q --skin=memcheck --leak-check=yes --leak-resolution=high
      --num-callers=100 --show-reachable=yes gdcmTests TestWriteSimple
      $(GDCMDATA_HOME)/012345.002.050.dcm foo.dcm