REVIEW [NX-485] move away from embedded dependencies

With these changes the full set of non-embedded bundles that make up Nexus can deploy and start on the Karaf assembly without import/export wiring problems. Note there are still a couple of launcher/configuration tasks to complete before this can be merged, as well as some cleanup of the build.

https://issues.sonatype.org/browse/NX-485 (depends on NX-432, but available for review)