setting property for common version in parent pom doesn't work - change to working alternative

The uimaj sdk build factors out the version number for dependencies on other uimaj artifacts. Having one spot in the parent pom makes this easy to change. But it doesn't work when it comes time to run the release:prepare step - the attempt to "rewrite" pom versions doesn't handle this case.

After some experimentation and googling, I found it will handle having the dependent version come from the common parent pom for uimaj, but just not from a custom property. Change to this approach:

1) still factor out the dependency to the parent, but make it the same as the parent pom's version.
2) change the version ref in the child poms to ${project.parent.version}.

This approach creates a tie between the normal dependency version for components, and the version of the common parent; since we're probably going to have all the components at the same version level anyways for a while, I don't think this is an issue, for now.