Add interface for Nifti-only datasets

[raamana]

for non-DICOM datasets (such as those from LONI IDA, HCP etc), key properties of MR volumes present only in NIfTI headers but NOT in JSON sidecars e.g., number of volumes, voxel size, image dimensions, and image obliquity... Hence, this also should be a format we support by default

[sinhaharsh]

Unless the dataset provides hierarchical information ( e.g. dataset, modality, subject, session) it would be difficult to organize NIfTI-only datasets for protocol compliance. The hierarchical organization is straightforward in BIDS dataset, but it may not be the same for other datasets such as from LONI IDA. For example, ADNI provides an XML file to store hierarchical information.

[sinhaharsh]

In addition, we need to discuss which of these properties should we expect to be compliant across subjects.

[raamana]

they are all coming from similar projects, so there is definitely correspondence, its a matter of us writing the datasets parsers and populating methods :). let's discuss that.