Customizable properties in MavenDependencyResolver

PicketLink integration testsuite uses MavenDependencyResolver to resolve test dependencies, but we need to customize properties when we're testing.
For instance we use sed to edit <version.picketlink> in pom.xml for now. It would be much more handy if we are able to provide customized properties to MavenDependency resolver and handle configuration without such hacks.

c.f.
our usage of the MavenDependencyResolver:
https://github.com/picketlink/picketlink-integration-tests/blob/master/unit-tests/util/src/test/java/org/picketlink/test/integration/util/MavenArtifactUtil.java

parent/pom.xml in which version.picketlink is defined
https://github.com/picketlink/picketlink-integration-tests/blob/master/parent/pom.xml

pom.xml for PicketLink integration tests (adds version.picketlink as system property to failsafe tests)
https://github.com/picketlink/picketlink-integration-tests/blob/master/integration-tests/pom.xml#L75