Added input size and read time.

This commit adds a new metric in TaskMetrics to record
the input size and read time when data is read from the BlockManager,
from HDFS, or from a parallelized collection, and displays this
information in the UI.
Made JobLogger more robust by improving log output.

Send exceptions to logError() rather than printing
a stack trace, and fail gracefully if JobLogger doesn't
start up correctly.
Fixed problems with tests
Add Job ID to job logger information