DataService - Add ability to batch actions (create, update, delete)

[tejaede]

This would accomplish 2 goals:

1. Simplify API when developer needs to work with many objects at once. (e.g. Promise.all() wouldn't be needed by the caller)
2. Enable implementation of Transactions

Phase 1

Batch actions of the same type

myService.saveDataObjects([objectToCreateA, objectToUpdateB, objectToUpdateC])

myService.deleteDataObjects([objectToDeleteD, objectToDeleteE, objectToDeleteF])

Phase 2

Batch actions of any type

// Either complete all of the below operations or rollback them all
myService.batch(
      myService.saveDataObjects([objectToCreateA, objectToUpdateB, objectToUpdateC]),
      myService.deleteDataObjects([objectToDeleteD, objectToDeleteE, objectToDeleteF])
)

The above snippets are meant to illustrate the use cases and are not meant to be interpreted as final method recommendations. Please suggest changes or alternatives freely below.