Stowrs chunked request

[hummerichsander]

Chunked STOW-RS upload

• New parser to handle chunked HTTP requests in STOW-RS view: The StowMultipartApplicationDicomParser now loads the uploaded datasets in chunks into memory and saves them individually once a dataset is fully read.
• ChunkedHTTPRequestMiddleware sets the CONTENT_LENGTH attribute of request.META to 1 for chunked HTTP requests. This is makes it possible that the Parser is also correctly used for chunked HTTP requests.
• Updated STOW-RS view response object: If the study_url arg is specified, the response dataset will have a top-level (study-level) RetrieveURL tag. Otherwise, only series level retrival urls are returned for the instances in the ReferencedSOPSequence.