Maven31DependencyGraphBuilder now resolves artifacts from within the reactor.

While applying this code to Maven3DependencyGraphBuilder is trivial it won't work because
in Maven 3, MavenProject.getProjectReferences isn't populated. So we would need to have the reactor
modules passed in separately which would change the API for DependencyGraphBuilder. If
MavenProject.getProjectReferences were populated (like it should be) then this would work for Maven3 too.

There doesn't seem to be any way to apply this to Maven2DependencyGraphBuilder as there is no
concept of partial resolution like there is is 3 and 3.1