Add ability to pass `das_client.py` options via `runTheMatrix.py`.

Similar to `--commands`, it is now possible to specify extra
das_client.py options via `--das-options`.

Usage of this includes, but is not limited to:

- Supporting cached queries, see also dmwm/DAS#4142.
- Running against a test bed instance.
Merge pull request #2420 from ktf/pass-options-to-das-client

Misc fixes -- Add ability to pass `das_client.py` options via `runTheMatrix.py`.
Merge remote branch 'origin/CMSSW_7_1_X' into CMSSW_7_0_X