Backport/3.0.x/use zinc artifacts published by dbuild

Backported POM changes to use dbuild's published Zinc artifacts. This change make our own [Sbt builds](https://jenkins.scala-ide.org:8496/jenkins/view/Sbt%20vs%20Trunk/) superseeded, and ready for archivation. Before merging this branch, I'm now going to make sure the uber-build can be used to build against this branch.