small improvement in ImportDicomFiles.py

Hi there,

Just wanted to give back a small improvement for ImportDicomFiles.py the script file provided by Orthanc to reimporte the dicom storage folder to a new orthanc instance.

the improvement is it now locally detecting if the candidate file is a json file and avoid calling the Orthanc POST instance API for a file that will obviously fail to be stored as dicom.

As orthanc storage folder has 50% of files being JSON this patch reduce by 50% the number of HTTP connexion made and thus improve significantly improve the speed of the reimport process.

I may do other improvement in this scripts so I put this on a public repository

https://github.com/salimkanoun/GaelO_Installation/blob/master/Maintenance/ImportDicomFiles.py

Best regards,

Salim