Implement automata "linking".

Automata can reference sub-automata, but in order to actually implement them we need to link those sub-automata in as concrete states and transitions.

As a by-product, fix the Manifest/Automaton memory model: the Manifest owns its Automaton instances.
A SubAutomatonTransition is not realisable.

This is why the linking thing was necessary!
Trivial: drop unused include.
Trivial: whitespace.