syncbase/vsync: add the sync DAG layer.

Add the sync DAG layer to store the history of object mutations,
use it to detect conflicts, and record conflict resolutions.

Change-Id: I52967a0b2626bf2fe5324081c64ff14059d566fa
14 files changed
tree: e364255c18717ca8d76cd07ec13152478ec3c22a
  1. services/