Fixed case comparison issue with model binding collections

Binding collections from request to model was running into an issue where request keys were being case capitalised prior to comparison, and thus values were not being bound - non-collection request keys were not running into the same issue as the comparison between capitalised key and request key was being done case insensitively.

Changed the comparison in the collection binding logic to do comparisons case insensitively to fix the issue.

Also changed String to string in same logic because @JChannon complained.