allow assigning values to nested dictionaries

[Jamiras]

Fixes an issue where modifying a nested dictionary did not work:

dict = {"a": {"b": 3} }
dict["a"]["b"] = 5
achievement("test", "test", dict["a"]["b"], trigger=...)

Would generate an achievement worth 3 points, not 5.

This is a result of the temporary variable used for storing dict["a"] evaluating the dictionary instead of referencing it. By evaluating it, a copy was made, and the ["b"] = 5 modification was applied to the copy.

The same problem occurs when using a non-anonymous intermediate variable:

dict = {"a": {"b": 3} }
t = dict["a"]
t["b"] = 5
achievement("test", "test", dict["a"]["b"], trigger=...)

t was a copy of dict["a"], so the modification was applied to the copy.

When dictionaries (or arrays) are passed to a function, they're done so by reference, so the function can modify the dictionary. I've extended that logic to do assignments of dictionaries (and arrays) by reference. As such, both t and the temporary variable in the first example are references to the nested dictionary, allowing the modification to go through.

NOTE: This eliminates the ability to copy a dictionary (or array) just through assignment:

function MergeArrays(arr1, arr2)
{
    newArr = arr1 // <-- this now creates a reference
    for i in arr2
    {
        array_push(newArr, i) // <-- so i is now actually being pushed onto arr1
    }
    return newArr
}

needs to be changed to:

function MergeArrays(arr1, arr2)
{
    newArr = []
    for i in arr1
    {
        array_push(newArr, i)
    }
    for i in arr2
    {
        array_push(newArr, i)
    }
    return newArr
}

This also provides a performance improvement when working with nested dictionaries as copies of the subdictionaries are no longer made just to pull values from them.