Add the ability to call the v1.1 of the REST API Endpoint on WordPress.com
Remove the static definition of BATCH_CALL_PREFIX but build it by using the Endpoint version.
Add the new rest client v1.1 to the WordPress app
Set the correct user-agent by using the default utility method, and remove unnecessary comments.
Merge pull request #1915 from wordpress-mobile/feature/REST-Client-v1-1

REST API Client V1.1