Adding some JNLP-signing infrastructure
Simplifying statement
Launching WebStart JNLPs through a shim '.jar'
Moving 'JNLPFileManager' to 'jnlp' package
Fixing obnoxious bug in `FileManager`

This bug has apparently been laying latent here for over a year.  How
nice!

Basically, it's something screwy with how Akka looks up actors.  You
give the actor a name with `system.actorOf(<blah>, name)`, but retrieve
it by name with `system.actorFor("/user/" + name)`, as if that makes any
sense....

Then, Akka's way of telling you that made the mistake of not
prefixing the name with `"/user/"` is to tell you that the actor you're
looking for "had already been terminated."  Thanks, Akka!
Adding 'public/shims' link

This will be used by the auto-'.jar'-signing infrastructure.
Fixing somehow-unhit bug in JNLP formatting
Changing determination of destinations of signed '.jar's

Previously, the output directory was being read from a configuration
property.  However, this ends up not working out so nicely.  In order to
be sufficiently general, the auto-signer ought to be able to output a
signed '.jar' to any location, as determined on the fly.  The property
wasn't all that useful, anyway....
Automatically signing JNLPs

NOTE: JNLPs that use a `codebase` attribute other than the default will
not be signed, for some fairly obvious security reasons.

This pre-emptively fixes an issue with Java, where it will soon be
disallowed to distribute unsigned JNLPs.  With the auto-signing in
place, we can continue to distribute our diversely-configured
WebStart applications as we have before, provided we use a signing
certificate from a root certificate authority.