Sync two XNAT instances

• The index.js is now implemented as a class library
• It is now possible to include the library to manipulate two XNAT instances.
• Retrieve any file from the XNAT instance as a stream
  -- Pipe the stream wherever you want, i.e., to a different XNAT instance .

Manipulate your xnat instance from the command line

This release allows operations to import dicom datasets, create resources, import converted images, change quality control labels.