Store arrays more efficiently

[Marwes]

Currently arrays are just stored as Array<Value> which wastes a lot of space as the tag information in the enum is duplicated. A better way would be to have multiple array types (Array, Array, Array and maybe even Array if a byte type were added).

Though the idea is straightforward the implementation may have some subtleties. For instance consider the following code

let twice x = [x, x]
twice 1
twice { x = 1 }

When constructing an array in the twice function the tag of x needs to be inspected so the correct array can be constructed. A similar problem comes when indexing an array where the code has to check the type of the array to construct the correct Value variant. Theses issues aren't to complicated but there may be other problems hiding as well.