Added a missing call to delete on the RegistrarProcess.
Renamed and moved MasterZooKeeperTest fixture.

Review: https://reviews.apache.org/r/20584
Integrated log storage into master.

Review: https://reviews.apache.org/r/20572/
Manipulated clock in metric tests to avoid rate limiting.

Review: https://reviews.apache.org/r/20642
Added message counters and a counter for slave timeouts during recovery in Master.

Review: https://reviews.apache.org/r/20638
Updated containerizer.proto's Launch message, added Destroy-, Wait- and Usage-messages.

Updated Launch message to reflect latest commits on the TaskInfo
related containerizer Launch call/s.  Added Destroy, Wait and Usage
messages to allow extending those messages in the future, where
needed.

Review: https://reviews.apache.org/r/20668