DatasetService: add method to wrap RAI to Dataset

It is useful to be able to wrap not just ImgPlus objects, but also any
RandomAccessibleInterval, to a Dataset.

This method will make it easier to display RandomAccessibleInterval
objects with ImageJ, beyond only ImgPlus and Img.
DefaultImageDisplay: refactor image class test

This change now has a dedicated method for testing whether a class is
compatible with the image display, for readability.
Dataset: remove redundant interface declaration
DefaultImageDisplay: support display of RAIs

We can now easily display any RandomAccessibleInterval, not just Data
objects, thanks to DatasetService#create(RandomAccessibleInterval).