Replace trampoline

trampoline is a fairly dodgy looking sudoish beast. It limits what we can do with stuff inside the jail, and provides no features to manage processes that it starts. It should be replaced with something better, more secure, and much more featureful.

Required features so far:
 - Starting an arbitrary process synchronously, like trampoline does now.
 - Starting, monitoring, and proxying connections to an asynchronous server, like python-console.