Fix up navtestbed-app-launcher

[rpavlik]

There's a lot more smarts in its counterpart that runs when launching navtestbed itself - should be split out into a module for command line processing, I suppose, since that's most of what the goodies are. Right now, it doesn't use the runbuffer (which should work on the cluster now, so no need to avoid it), doesn't do cluster init for vrj 3.0, etc. (Hasn't really been touched since using it for shopping cart study, which we did very early on and with juggler 2.2)

[rpavlik]

cc @jscasallas