Add initial support for reading BinaryOnly OME-TIFF datasets

This adjusts the type detection slightly so that .companion.ome files
are detected as OME-TIFF, not OME-XML (as this makes finding and reading
the corresponding OME-TIFF files much easier).  Selecting either a
BinaryOnly OME-TIFF file or the corresponding companion OME-XML file
should result in the entire dataset being read.

Fixes https://trac.openmicroscopy.org.uk/ome/ticket/11951.  Sample files were generated from gh-1015, and are in ```data_repo/from_skyking/ome-tiff/samples/binary-only```.