[Dcmlib] force loading elements

[Jean-Pierre Roux]

Hi!

According to some users requirement, we can now force the loading of 
some elements whose length exceeds the current MAX_SIZE_LOAD_ELEMENT_VALUE.

use it as :
      gdcm::File *f = new gdcm::File();
      f->SetLoadMode(loadMode);
      f->SetFileName( fileName );
      f->AddForceLoadElement(0x0029,0x1010);
      f->AddForceLoadElement(0x0028,0x1020);
      bool res = f->Load();

Check it with :

PrintFile filein=wereInGdcmData/MR_forceLoad29-1010_29-1020.dcm  
forceload=29-1010,29-1020

JP