[Dcmlib] Serie Helper

[Mathieu Malaterre]

> --> For application reasons of their own, some users wish to 'order' , 
> using  OrderFileList() method -or the next one-, not a
> std::vector(<gdcm::File*>)             - typedefed, right now as 
> gdcm::FileList -
> but a
> gdcm::DicomDirSerie                    - that's, right now, a 
> std::list(<gdcm::DicomDirImage *>) -
> 
> gdcm::File inherits from gdcm::Document
> DicomDirImage inherits from gdcm::SQItem
> Both gdcm::Document and gdcm::SQItem inherits from gdcm::DocEntrySet.
> All the low level methods to access the gdcm::DocEntries to perform the 
> comparison operations are available at the gdcm::DocEntrySet level(no pb 
> till here), the iterators work the same way for both std::vector and 
> std::list
> but the 'Added Value Methods', say : GetImageOrientationPatient, 
> GetXOrigin, GetYOrigin, GetZOrigin are only defined for gdcm;;File (they 
> are meaningless for, say a gdcm::DicomDir, or any kind of gdcm::SQItem), 
> but there are fully meaningfull (?) for a gdcm::DicomDirImage.
> It would be silly to nove theses methods up to gdcm::DocEntrySet.
> Using template method hang at  *application* compile time

I need more time to answer this one...