[NX-450] Component Sources & Raw Hosted/Proxy Views

JIRA: https://issues.sonatype.org/browse/NX-450
Having thought about this a bit, I think out-of-service sources should stay in the source list, so we don't need to do anything to the views that are referring to them.  I'm going to elaborate on this in a follow-up PR that will also deal with the lifecycle issues of sources going away while views are still referring to them and all that stuff.