POM: exclude com.sun:tools from the enforcer check

Otherwise, it is not possible to build with JDK7 or JDK8.
Update to the ImgLib2 2.0.2 release

This bumps pom-imagej to the latest version (3.2),
and furthermore, updates a couple of components further:

* imagej-ui-awt -> 0.2.0
* imglib2 -> 2.0.2
* scifio -> 0.17.0

It also makes the necessary code changes to adjust for
the backwards incompatibilities of the ImgLib2 release.