According to Benoit's suggestion, and without any objection from anybody

According to Benoit's suggestion, and without any objection from anybody
- methods SetxxxByNumber and GetxxxByNumber renamed as Setxxx and Get xxx
- methods Dict::Print() and Dict::PrintByKey() merged into Dict::Print()
- method gdcmDicomDirObject::GetEntry() renamed as
         gdcmDicomDirObject::GetEntryHT() to avoid confusion (and compile error)