Added execution summary, modified benchmark to handle JSON

- Added execution summary to the beeswax client and QueryResult
- Modified report-benchmark-results to handle JSON and perform
  execution summary comparison between runs
- Added comments to the new workload runner

Change-Id: I9c3c5f2fdc5d8d1e70022c4077334bc44e3a2d1d
Reviewed-on: http://gerrit.ent.cloudera.com:8080/3598
Reviewed-by: Taras Bobrovytsky <tbobrovytsky@cloudera.com>
Tested-by: jenkins
Modified Case expression tests in exprs.test

Change-Id: I65cee2e14291db8bf14a428715b08dac475b863a
Reviewed-on: http://gerrit.ent.cloudera.com:8080/3485
Reviewed-by: Paden Tomasello <paden.tomasello@cloudera.com>
Tested-by: jenkins
IMPALA-1080: Implement "SET <query_option>" as SQL statement.

Also add support for "SET", which returns a table of query options and
their respective values.

The front-end parses the option into a (key, value) pair and then the
existing backend logic is used to set the option, or return the result
sets.

Change-Id: I40dbd98537e2a73bdd5b27d8b2575a2fe6f8295b
Reviewed-on: http://gerrit.ent.cloudera.com:8080/3582
Reviewed-by: Daniel Hecht <dhecht@cloudera.com>
Tested-by: jenkins