Use linked lists

[harrytallbelt]

The current take on program specification uses arrays to store invariants, boundary functions, result predicates, and context objects. (Double?) linked list seem to better suit this task, because we do not need random access, but do want persistent slices when adding/removing first/last elements.

The program representation also uses arrays, while it probably can also benefit from lists.

The suggested package is this one: https://www.npmjs.com/package/yallist

Note that:

• this is not performance critical right now,
• but may result in a better looking code (without so much array copying).