Support individual component version release

[hinerm]

This repository is structured as a multi-module Maven project except that each "module" is treated as distinct and inherits from pom-scijava instead of a single reactor pom.xml in the project.

For the initial release of SciJava Ops we were able to get away with keeping all intra-repo dependencies at project.version because each project was at the same 1.0.0 version. However, this left us with technical debt for releasing future individual components. We do not want to bump all component versions each time a single component needs release, as this creates a large amount of vacuous releases that are likely meaningless and violate (or at least mislead) SemVer.

First requirement, as standalone projects:

• All individual projects should have entries in the dependencyManagement section of the pom-scijava bill of materials, with appropriately named component.version properties defined.

Problem 1:
Unfortunately, although these projects should be managed in pom-scijava, these are all release versions. Within the reactor we still want SNAPSHOT versions for these dependencies so that changes in one are immediately reflected in another, thus we can't actually use the component.version properties inherited from pom-scijava.
Discussion point: is this a technical requirement or one of convenience? If we keep everything release-coupled, the development process would be no different than if the projects were in separate repositories (e.g. manually pinning to SNAPSHOTs or "fake" versions for local testing) and we wouldn't have to worry about the enforcer, right?

Problem 2:
The maven-release plugin, and our release-version.sh script, don't support releasing individual components out of a multi-module reactor. Therefore we currently have no way to actually perform component releases reliably.

Second requirement:

• Create a new release script, for a single component in a multi-module reactor:
  • Manually performs any required maven-release steps
  • Creates a component-name-component-version tag with the release commit
  • Updates version properties in other components?'
  • ... what else?

[gselzer]

• All individual projects should have entries in the dependencyManagement section of the pom-scijava bill of materials, with appropriately named component.version properties defined.

I added these with scijava/pom-scijava#282, however the build fails due to the projects being built on Java 11 ☹