Bootstrap netlet

A netlet which is given to Jnode on the command line for it to run.

Jnode runs each bootstrap netlet in turn, then continues running so the netlets can continue their work. Jnode also endows each bootstrap netlet with the ability to access file I/O streams, also specified on its command line. This enables them to perform their own specific tasks (e.g. reading a warrant or writing a descriptor) without having the complete system access that an external netlet is given.