[SPARK-2318] When exiting on a signal, print the signal name first.

Author: Reynold Xin <rxin@apache.org>

Closes #1260 from rxin/signalhandler1 and squashes the following commits:

8e73552 [Reynold Xin] Uh add Logging back in ApplicationMaster.
0402ba8 [Reynold Xin] Synchronize SignalLogger.register.
dc70705 [Reynold Xin] Added SignalLogger to YARN ApplicationMaster.
79a21b4 [Reynold Xin] Added license header.
0da052c [Reynold Xin] Added the SignalLogger itself.
e587d2e [Reynold Xin] [SPARK-2318] When exiting on a signal, print the signal name first.
SPARK-2293. Replace RDD.zip usage by map with predict inside.

This is the only occurrence of this pattern in the examples that needs to be replaced. It only addresses the example change.

Author: Sean Owen <sowen@cloudera.com>

Closes #1250 from srowen/SPARK-2293 and squashes the following commits:

6b1b28c [Sean Owen] Compute prediction-and-label RDD directly rather than by zipping, for efficiency