Migrate missing features and fixes from old SDK

**Topic for discussion**

It is pity that we hit same [issues](https://github.com/commercetools/nodejs/pull/590) with new SDK which has been addressed in [old SDK](https://github.com/sphereio/sphere-node-sdk/blob/master/src/coffee/sync/product-sync.coffee#L44-L56) already as for existing customers migration might be a costly enterprise as they might hit issues that were not present with old SDK. The reason is obviously that rewrite of new SDK was based on old SDK and as it took around 1 year of development all the fixes/features applied to old SDK during that time were not migrated to the new SDK release.

**Suggestion**

Review all issues/PRs/commits from old SDK implemented after rewrite fork and create a list of TODOs for migration like examples below.

**Missing fixes/features**
- [ ] - Sync actions should first [remove variants](https://github.com/sphereio/sphere-node-sdk/blob/master/src/coffee/sync/product-sync.coffee#L45)
- [ ] - fetch all [convenience function](https://github.com/sphereio/sphere-node-sdk/blob/master/src/coffee/services/base.coffee#L227) for multi-paged results
- [ ] - GraphQL convenience method which allows to do GraphQL requests with single line instead of boiler plate utils in every project
- [ ] - Provide GraphQL process function for paginated results and fetch all if one needs to load all paginated results into memory.

Examinez les anciennes références au SDK dans src/coffee/sync/product-sync.coffee et src/coffee/services/base.coffee, ainsi que le PR 590 associé. Comparez les issues, PRs et commits postérieurs au fork avec le nouveau SDK, puis documentez les corrections et fonctionnalités manquantes sous la forme d’une liste TODO de migration ; la tâche sera terminée lorsqu’une liste vérifiée et exploitable couvrant les exemples de l’issue sera disponible.

Rédigé par le modèle d'indexation à partir du texte de l'issue.