Root path of BaseFOV

[ziw-liu]

In #132 the BaseFOV.root returns a pathlib.Path object and __eq__ compares the paths of two FOVs to check if they are the same. This assumes that an FOV always has a single path. However in OME-TIFF and NDTIFF one FOV can be distributed in many TIFF files (usually a subset of all the TIFF files in the dataset).
Edit: the same file can also contain multiple FOVs.

@JoOkuma Should we change this or is there a way around it?

[ziw-liu]

Also for OME-TIFF and NDTIFF it is cumbersome for the FOV objects to carry state of the index map, because parsing has to happen at the dataset (BaseFOVMapping) level.