Usecase: I've removed unused classes from a JAR using Proguard but it seems I've been too aggressive so the application
fails at runtime. In order for me to figure out what classes I need to put back in I need to be able to start a
debugging session against an existing JAR file.

Essentially this means that I want Netbeans to take an existing project, keep the source-code configuration but allow me
to override some parts of the classpath. Probably the easiest way to implement this would be to add a "Debug Other"
option that allows users to specify a classpath prefix before beginning a debugging session. This would behave similar
to Profile -> Profile Other in the sense that the configuration would only apply to a single session (as opposed to
altering the behavior of normal debugging sessions).