omni file -> Dataset reader

[mdoube]

Need a utility method to read XamFlow omni files off disk and onto the Java heap, as byte[] backed Dataset with ImageJ unsigned 8-bit (0,255) (00000000, FFFFFFFF) binary convention.

[mdoube]

omni uses 0 and 1 for binary images, so a conversion is needed.

[mdoube]

RAW file reading is working, from #413 . An enhancement would be to load the .omni JSON file and use the metadata for creating the Dataset.