Feature: Implement map, filter, fold, head, tail, reverse, cons ::

[Spicylemon2623]

Add the above features to Calyxium as built-ins

[PeterGriffinSr]

Currently implemented:

• Head
• Tail
• Reverse
• Fst
• Snd

Need implementation:

• Map
• Filter
• Fold
• Cons (::)