supporting validation for GetMyFeesEstimate requires support for object parameters

[ericblade]

GetMyFeesEstimate is expecting a list of keys that would look a bit in code like:

                // FeesEstimateRequestList.FeesEstimateRequest.1=
                // {
                //     IdType: 'ASIN', // type: 'MarketplaceType', values: ['ASIN', 'SellerSKU'],
                //     IdValue: 'B002KT3XQM', // type: 'xs:string'
                //     IsAmazonFulled: true, // type: 'xs:boolean',
                //     Identifier: 'request1', // type: 'xs:string'
                //     PriceToEstimateFees: {
                //         ListingPrice: {
                //             CurrencyCode: 'USD',
                //             Amount: '30.00',
                //         },
                //         Shipping: {
                //             CurrencyCode: 'USD',
                //             Amount: '3.99',
                //         },
                //         Points: {
                //             PointsNumber: 0,
                //         },
                //     },
                // }

... this taken from comments i've made in products.js.