Titan implementation improves
Merge branch 'master' of https://github.com/felipeko/linkbench

# By Tim Armstrong (10) and others
# Via Tim Armstrong (3) and others
* 'master' of https://github.com/felipeko/linkbench:
  Merge remote-tracking branch 'remotes/facebook/master'
  beta mongo e mysql
  get linkbench working with rocks db
  Use 2 connections per client -- read-write, read-only. This avoids the need to send "commit" for queries. This also lets InnoDB use its fast-path for read-only transactions (SELECT when in auto-commit mode). And it reduces the number of statements that are run (fewer COMMIT calls are made).
  Minor fix of requester statistics
  Fix corner case where hidden link is expunged
  Fix potential race condition with delete.  Document ACID.
  Fix genNode to fill version and time in right field.
  Consistent handling of link count version and timestamp
  Specify locale for distribution file scanner.
  Document assumptions about node ID allocation more clearly
  Convert LinkBench to use maven
  Improve test running with maven
  Make maven happier by specifying version
  Document fields of Link/Node
  Add more meaningful error messages to RealDistribution when loading from file