Add support for arrays

[blaumeise20]

We should add support for arrays! They would allow us to create complex structures.

Changes:

Restructure for loops to iterate over an array:

for <variableName> of <array> 
{
}

to would create an array:

var nums: int[] = 1 to 10
for i of nums
{
}

Function array(length: number): any[]:

let list: string[] = array(5)

To make that possible we would also have to implement nulls (#171)
Function count(list: any[]): int

let length: int = count(list)

New syntax [0, 1] to create initialized arrays (automatically detect types):

let list2 = [1, 2, 3, 4, 5] // I know, you could use 1 to 5 here

New syntax list[i]:

let value = list2[2] // = 3

That would allow us to create such functions:

function prompt(questions: string[]): string[]
{
    let result: string[] = array(count(questions))
    var index = 0;
    for q of questions
    {
        print(q)
        result[index] = input()
        index++ // I think we already have that
    }
    return result
}

[HirushaR]

Does someone working on arryas