GIRAPH-976: More command line logging

Summary:
Add more logging to command line:
- if a worker fails log which worker failed
- if some worker is low on memory, warn user about it

Test Plan:
Run a job where worker fails, saw:
  FATAL   2014-12-29 11:29:25,879 ******* WORKERS [Worker(hostname=hadoop5247.frc1.facebook.com, MRtaskID=2, port=30002)] FAILED *******
Run a job low on memory, saw:
  INFO    2014-12-29 11:40:55,731 Data from 5 workers - Compute superstep 0: 1040758 out of 1302981 vertices computed; 20 out of 25 partitions computed; min free memory on worker 2 - 3775.79MB, average 94126.79MB, ******* YOUR JOB IS RUNNING LOW ON MEMORY *******
Run normal job verified everything is as before.

Reviewers: pavanka, sergey.edunov

Differential Revision: https://reviews.facebook.net/D30729