Extend pom-imagej 5.0

This brings in the latest versions of SciJava components,
particularly the release version of imglib2.
Remove superfluous version declaration

The scijava-maven-plugin's version is managed in the parent.
Remove superfluous distributionManagement section

You can pass the -Pdeploy-to-imagej flag if you want to deploy to there.
Remove superfluous maven-compiler-plugin version

It is managed in the parent.
Declare all version properties as release versions

At the time of this writing, some of these projects have not actually
been released at those versions. Hence, it is a preemptive version bump.
Remove obsolete projects

These version numbers are no longer declared, and hence
the version management declarations are not useful.
Bump fiji-lib to 2.1.0

The 2.0.1 release is invalid.
Bump 3D_Viewer version to 3.0.0