Path to POPL paper formalisation

[MatthewDaggitt]

Need:

1. Add universal quantifier to MiniVehicle.
2. Add vector folds to MiniVehicle.
3. Add vector quantification to and normalise variables to sequences of scalar variables.
4. Add true and false literals.
5. Vector literals

Optional extras:

• Avoid normalising vectors, if possible.
• Add Gaussian elimination.