Keepa

New offer field maxOrderQty added

New fields for the product finder request and seller object.

The _monthlySold_ and _lastSoldUpdate_ fields were added to the product object.

The _referralFeePercent_ field was added to the product object.

- added sendRequestWithRetry with custom timeouts
- added singleVariation to DealsRequest
- added primeExclCSV to Offer
- added buyBoxUsedHistory to Product
- added BUY_BOX_USED_SHIPPING and PRIME_EXCL to CsvType
- removed deprecated fields from ProductFinderRequest and added new ones
- added new fields to Seller
- added Buy Box Used related fields to Stats
- updated dependencies and removed incorrect javadoc.