Move dicoms to subdir

[CGDogan]

UI: camicroscope/caMicroscope#655

1. Accept relative paths through our rest api where it makes sense
2. calculate a hash for dicom files and move them to the directory

which should solve the problem that camicroscope is too slow when birm opened dicom files.

tested batchupload, normal uploader, download slide button

[birm]

👍

[birm]

Actually, now that I've merged, it doesn't seem like all of the loaded slides were added to a directory.
Here are two dicom files I used batchloader on at the same time:

[CGDogan]

Some DICOM files are expected to be opened at the same time - WSI DICOM files which have multiple layers. Some are one file = one image. OpenSlide test directory has those that are read together https://openslide.cs.cmu.edu/download/openslide-testdata/DICOM/ and you can even use single file upload mode to upload them one by one as the order or method of upload doesn't matter, folder ID is inferred from image metadata inside dicom file. Separation of folders prevents the super slow loading bug you've experienced and by inferring from dicom files, we don't assume that the user will use a particular upload method. Great idea I think - belongs to Tony.