Support Event/Listener style callbacks

A interesting feature would be to be able to add listeners for events on ContainerTypes or paths.

/META-INF/* or all events generated via ClassContainer

usecase 1, if/when we add something like a ManifestDescriptor, instead of having it like the WebArchiveDescriptor.addServlet, adding a addMenifestLibrary that delegates down to addLibrary and update the 'classpath: ' manifest entry.. we could register a listener on the LibraryContainer and get callbacks when a 'normal' addLibrary happens

usecase 2, could deploy a 'live' archive to embedded.. one could register a listener on all changes in the archive and auto redeploy it on events..
deploy it once, redeploy on change