Disabled 'tasks.json' route in master due to MESOS-979.

Review: https://reviews.apache.org/r/17924
Fixed flaky FaultToleranceTest.IgnoreKillTaskFromUnregisteredFramework.

Review: https://reviews.apache.org/r/17928
Added 'hostname' flag to the master.

Review: https://reviews.apache.org/r/17210
Added 'protobuf::createMasterInfo()' to create MasterInfo from UPID.

Review: https://reviews.apache.org/r/17572
Changed master and slave to get the default hostname based on the ip.

Review: https://reviews.apache.org/r/17573
Updated detector to return MasterInfo instead of PID.

Review: https://reviews.apache.org/r/17574
Updated master redirection to use leading master's hostname.

Review: https://reviews.apache.org/r/17575
Fixed AWAIT_* macros which can hang forever if the Clock is paused.

- Note that this fix acts as a safeguard to prevent AWAIT_* in tests
  running forever. It does not eliminate the need to advance the clock
  in loops in some tests.
- I found putting Clock::advance() (optionally with os::sleep) in
  AWAIT_* too implicit and takes control over the clock from
  developers who write tests. (See related ticket
  https://issues.apache.org/jira/browse/MESOS-827, will explain
  elsewhere.)

Review: https://reviews.apache.org/r/17805
Removed the while loops in ZooKeeperTest.

Review: https://reviews.apache.org/r/17806
Made Group's state transitions monotonic except when expiration occurs,
in which case it is reset to the initial state (DISCONNECTED).

- Reconnecting does not reset the state to CONNECTING now. The steps
  the group has taken to set up the group are remembered (thus not
  redone) across reconnections.
- Improved comments on state transitions.
- Added the DISCONNECTED state back for the parity between Group and
  ZooKeeperStorage.

Review: https://reviews.apache.org/r/17858
Fixed flaky MasterZooKeeperTest.LostZooKeeperCluster.

Review: https://reviews.apache.org/r/17864
Removed an unnecessary intermediate ZooKeeper WatcherProcess.

Review: https://reviews.apache.org/r/17440
Logged Mesos version in master, slave and drivers.

Review: https://reviews.apache.org/r/17952
Disabled IO.BlockingWrite until MESOS-973 is fixed.
Fixed tests to properly set slave hostname when using whitelist.

Review: https://reviews.apache.org/r/17969
Revise os::killtree semantics if process not found.

Change semantics so it is not an error if the process is not found.

Review: https://reviews.apache.org/r/17953
Added missing return value for hashmap::containsValue and test.

Review: https://reviews.apache.org/r/17834
Containerizer (part 1)

The proposed Containerizer interface is to replace the existing
Isolator.

One ContainerizerProcess has been written:
MesosContainerizerProcess - implements containerizeration internally
using a Launcher and one or more Isolators (following review)

The intent is to also support a generic ExternalContainerizerProcess
that can delegate containerizeration by making external calls. Other
Containerizers could interface with specific external containerization
techniques such as Docker or LXC.

Review: https://reviews.apache.org/r/16147
Containerizer - launchers (part 2).

Launcher interface and MesosLauncher to support MesosContainerizers.

Launchers handle the lifecycle of the executor process
(and descendants).

Review: https://reviews.apache.org/r/16149
Containerizer - isolators (part 3).

Isolators perform isolator for the MesosContainerizer.

Isolator interface and implementations of Posix CPU and Mem isolators
(no isolation, just usage())

Review: https://reviews.apache.org/r/16150