POM: fix package prefix
POM: add missing dep: imglib2 tests classifier

The net.imglib2.util.ImgTestHelper class is used in the unit tests,
and it is only available from the imglib2 tests classifier artifact.
Remove unused ImgLib2Display class

This class makes use of the deprecated OrthoSliceCursor which has been
removed in the ImgLib2 2.0.1 release. I checked, and nothing in the
imglib or imagej orgs makes use of this class.
POM: update to imglib2 2.0.1 release

This commit also makes the necessary code changes to account
for the backwards incompatibilities of the ImgLib2 release.