Implement Possibility to send several object on one API request / BULK

[nuzil]

We have to implement possibility to accept in REST Requests body multiple entities.

Acceptance Criteria:

• In BODY of POST / PUT or DELETE Request we can submit multiple entities in one call
• Magento have to be able accept such request, split is to simple operations and process this request like BULK request but with single operations
• Statuses of those operations have to be able to get with "status" request