Update FoxyCart getters/setters

Update FoxyCart to have proper getters/setters for private variables
Update foxycart.cart_validation to properly get/set private variables
Update FoxyCartTemplate_Controller to use proper getter to get store name
Update FoxyCartTemplate_Controller to use non-deprecated function to get theme directory
Update FoxyCart.php to remove debug call
Update foxycart.cart_validation.php to remove debug call
Update FoxyCart.php to throw error if $foxyCartStoreName isn't set
Update FoxyCart.php to handle null store name and key
Merge pull request #11 from nhorstmeier/foxyCartValidation

Update FoxyCart getters/setters