Support the new API workflow for posting commit series

Review Request #10240 — Created Oct. 18, 2018 and submitted — Latest diff uploaded

Information

RBTools
master
63df254...

Reviewers

RBTools now uploads a cumulative diff of the entire commit series after
all commits have been uploaded so (a) Review Board can have a copy of
this diff instead of generating it and (b) Review Board can validate
the uploaded commits fully represent the range uploaded.

Posted a commit series for review and then published it. It worked!