mattdrayer/api-users-courses-batch: Submit multiple content positions to...

...gether

@chrisndodge @martynjames -- batch submission of course content positions to support MCKIN-1987 -- take a look and let me know what you think.

As Chris noted in JIRA, this will require a modification on the Apros side due to the move to using an array as the request/response container for position data.