ExecSummary

The runtime profile as we present it is not very useful and I think the structure of
it makes it hard to consume. This patch adds a new client facing schemed set of
counters that are collected from the runtime profiles. For example, with this structure
it would be easy to have the shell get the stats of a running query and print a useful
progress report or to check the most relevant metrics for diagnosing issues.

Here's an example of the output for one of the tpch queries:
Operator              #Hosts   Avg Time   Max Time    #Rows  Est. #Rows  Peak Mem  Est. Peak Mem  Detail
------------------------------------------------------------------------------------------------------------------------
09:MERGING-EXCHANGE        1   79.738us   79.738us        5           5         0        -1.00 B  UNPARTITIONED
05:TOP-N                   3   84.693us   88.810us        5           5  12.00 KB       120.00 B
04:AGGREGATE               3    5.263ms    6.432ms        5           5  44.00 KB       10.00 MB  MERGE FINALIZE
08:AGGREGATE               3   16.659ms   27.444ms   52.52K     600.12K   3.20 MB       15.11 MB  MERGE
07:EXCHANGE                3    2.644ms      5.1ms   52.52K     600.12K         0              0  HASH(o_orderpriority)
03:AGGREGATE               3  342.913ms  966.291ms   52.52K     600.12K  10.80 MB       15.11 MB
02:HASH JOIN               3    2s165ms    2s171ms  144.87K     600.12K  13.63 MB      941.01 KB  INNER JOIN, BROADCAST
|--06:EXCHANGE             3    8.296ms    8.692ms   57.22K      15.00K         0              0  BROADCAST
|  01:SCAN HDFS            2    1s412ms    1s978ms   57.22K      15.00K  24.21 MB      176.00 MB  tpch.orders o
00:SCAN HDFS               3    8s032ms    8s558ms    3.79M     600.12K  32.29 MB      264.00 MB  tpch.lineitem l

Change-Id: Iaad4b9dd577c375006313f19442bee6d3e27246a
Reviewed-on: http://gerrit.ent.cloudera.com:8080/2102
Tested-by: jenkins
Reviewed-by: Nong Li <nong@cloudera.com>