Updates to TIFF stack handling

[ruven]

Updates to build_stack.py script to:

1. Embed info.json into ImageDescription instead of XMP field as this was creating compatibility problems with some imaging software due to non-conformant XML content within XMP field. This now also aligns with the tag used by OME-TIFF.
2. Embed spatial resolution information within TIFF
3. Add new tile size parameter

Update to relight.js when using IIP layout to:

1. Use updated TIFF field to retrieve info.json file
2. Use info.json's format string to determine which kind of tile request to make (useful for switching to WebP if WebP compression has been used within TIFF)

[ponchio]

Looks fine, thanks.