Initial version of I2I reader

See http://trac.openmicroscopy.org.uk/ome/ticket/12426.

To test, first copy the ```*.class``` files from ```data_repo/from_skyking/i2i/IJ plug-ins``` into the ImageJ plugins directory.  Then verify that each of the two ```.i2i``` files in ```data_repo/from_skyking/i2i/sample files``` opens identically in ImageJ using ```Plugins > open i2i``` and Bio-Formats.

Note that very little metadata is present in these files, so checking the pixel data is sufficient.