Add Support for Array Multiselect

Instead of `foo.{bar,baz}`, you can instead say: `foo.[bar,baz]`.

This will return a list instead of a dict.

The benefit here is that order is guaranteed because we're creating a list.

There's potential for a syntax that's not available in multiselect with a dict, being able to recursively index into a list: `foo.[[0][0][0][0]]`.  This is certainly possible to support, but I'd like to keep it simple for now until there's a definite need for this.