Add a goal to update the versions listed as properties in a given parent pom

[dscho]

We used to call a helper script called bump-pom-scijava.sh to update the versions in pom-scijava. This was a bit fragile, and we can do much better than that if we use full-blown Java instead of hacky shell scripting.

The logical place for the code to do the job is the scijava-maven-plugin.

[dscho]

The helper was renamed to bump-versions-in-pom.sh.

[ctrueden]

We do not always want to bump all versions to the latest; the point of pom-scijava is to ensure all the versions are compatible, not latest. We now have https://status.scijava.org to fully report on the situation, including which dependencies could be bumped, and which ones could use a new release based on their SNAPSHOT status.

As such, we no longer need to make any improvements to scijava-maven-plugin along these lines.

Relatedly: the versions-maven-plugin can be used to report which plugins and/or dependencies have newer versions, via the versions:display-plugin-updates and versions:display-dependency-updates, respectively. (Passing -U with them seems to work more reliably, in my experience.)