Add prefer SR option to MG and DX DICOM queries

[Ed McDonagh]

Refs #464 and #368

Currently I think the behaviour would be to retrieve the DX/CR/MG images and the RDSR if there was one, then it would be a case of which one was imported first.

Add an option to the command line and web interface to allow the user to prefer RDSR, ie if there is an SR in the modalities in study list, only retrieve that.

However, if there were sites where other structured reports were in the same study UID, then this would mean that SR was retrieved alone meaning nothing was imported. Hence why it needs to be an option.

Can't immediately think of a better way of distinguishing this situation for sites that have RDSR producing DX or MG that also have other SR objects with the same study UID. I also don't know how prevalent this is!

[Ed McDonagh]

QR overhaul fixes #466. #468, #470, #473, #475

→ <<cset 3ce6ef2b48d5>>