Fixed reading/writing arrays through model

Before the fix doing this:

```
var array = [1, 2, 3];
console.log(array);
myModelObject.array = array
console.log(myModelObject.array);
```

would print this:

```
[1, 2, 3]
[ [1, 2, 3] ]
```

After the fix the arrays are correctly assigned and the example above prints out:

```
[1, 2, 3]
[1, 2, 3]
```

Furthermore, storing such an array into the database was working correctly but retrieval of arrays was adding bogus "id" fields and converting values like strings from "123" into objects like { "123", id: 1 }. To make the matters worse this was applied to all the items in arrays.

I didn't find any better solution that to simply skip creating ListItem objects for Arrays. To be honest I suspect that there is a good reason to insert those "id"s but for me it was simply corrupting the data.

Finally, I changed the original commit to work, I think, more cleanly with arrays in lists, reading and setting them in list.items property.