Support new product REST API pagination

[rjdavis3]

https://help.shopify.com/en/api/guides/paginated-rest-results#supported-endpoints

The July 2019 Shopify API release deprecated pagination via page numbers in favor of pagination by using links that are proved in the response header:
https://help.shopify.com/en/api/reference/products/product#index-2019-07

Currently the shopify-sdk will log an ERROR level message when making getProducts calls indicating the deprecated header.

Looks like we have been moved back to X-Shopify-API-Version=[2019-04] for these requests (we are not currently specifying a version in our API requests).

Therefore since this is the only deprecated call we are currently making, according to the API version releases schedule we have until 2020-04 to upgrade our services with the new product pagination.

https://help.shopify.com/en/api/versioning

Each stable version is supported for a minimum of 12 months. This means that there are at least 9 months of overlap between two consecutive stable versions. When a new stable version is introduced and contains changes that affect your app, you have 9 months to test and migrate your app to the new version before support for the previous version is removed.

[rjdavis3]

Implemented by 2.0.0 release.