Support multi-dimensional array comma access syntax

[TwitchBronBron]

Apparently multi-dimensional arrays support using a comma to access sub levels, rather than [idx][idx].
The parser currently fails with this syntax.

Here's some examples:

myMultiArray = [["hello"]]

'currently supported syntax
print myMultiArray[0][0]
'currently broken syntax
print myMultiArray[0, 0]

This seems to work for however many levels of nesting you have.

myMultiArray = [[[[[[[[["hello"]]]]]]]]]
print myMultiArray[0][0][0][0][0][0][0][0][0]
print myMultiArray[0, 0, 0, 0, 0, 0, 0, 0, 0]