Support arrays in grammar about prism-interpreter

[harsath]

It should support:

• Array initialization, ex: INT[10] foo = {1, 2, 3, 4, 5} (we can insert up to 10, but throws exception when we insert more).
• Array reference, ex: INT foobar = foo[2] (refers to value 3).
• Array assignment, ex: foo[1] = 100 (now array looks like {1, 100, 3, 4, ...}
• Functions should take arrays as arguments, like FUNCTION foobar_fn(INT[] hey, BOOL hello) { ... }
• For getting the size of array, capacity, etc. we will have builtin functions, something like python, len(some_array) and it returns the total size, or we can do array_var.SIZE() to get size. We will discuss on the design choice once we get the basics done.