Enhancements in donwload series function:
1. Ability to download series only on demand.
2. Start/stop buttons on each thumbnail.
Fix sorting issue in download priorities
Add stop/resume in global processing. Fix global download order. Fix
resizing thumbnail issues. Fix open series with no image. Start to
improve dicom reading options.
Separate executor for downloading and for dicomdir
Allow scrolling when the series contains corrupted images
Handle several image decoders for DICOM tsuid
Separate SR viewer in a project
Make fully generic for adding viewer for non image dicom (SR, ECG...).
Use official dcm4che 3.3.1 release