Sync and merge next steps

[josephjclark]

Outstanding work on the sync, sandbox and merge APIs which needs resolving quickly

The documentation is a really important step and a validation of the design. That probably needs doing first.

[josephjclark]

possibly include: I've just moticed in merge-project that we don't set onlyUpdated. I think by default the merge should only do updated. But if workflows is passed this is false.