create group policy validation bugfix

When multiple policies are sent in create group request, only first policy was getting validated but the whole
request was getting stored. When scheduler policy is processed it causes exception and 500 error.

Changed to validate all elements in the array. Please see
http://tools.ietf.org/html/draft-zyp-json-schema-03#section-5.5
added negative test - create group with multi policy invalid request
Merge branch 'master' into test-to-validate-multiple-policy-request
Cleanup get_metrics method.

Formatting only happens on a single result, and association between
field and label is now easier to maintain.
Job failure logged as msg

Since its not really an otter error. Moreover, otter tried its level
best to fix it before failing
Change wording for variables in `get_metrics`.

Everywhere else uses table(s) to reference which tables data is coming
from. Creatting an intermediate variable `mapping` makes the list
comprehention a little clearer.
Consume errors when querying Cass. for metrics.
Change `get_metrics` to query correct table.

`scaling_config` was changed over a month ago to `scaling_group`.
Reflecting this in `get_metrics` and tests.
review
Merge branch 'master' into test-to-validate-multiple-policy-request
tests added for create_group validation
Merge pull request #368 from rackerlabs/create_group_validation

create group policy validation bugfix
changed tags to quick
Merge pull request #370 from rackerlabs/test-to-validate-multiple-policy-request

test-to-validate-miltiple-policy-request (ready for review)
Merge pull request #377 from rackerlabs/cleanup-get-metrics

Cleanup get_metrics method.
fix group min
Merge pull request #383 from rackerlabs/fix-create-group-min

fix group min (ready for review)
Merge pull request #380 from rackerlabs/job_log_msg

Job failure logged as msg
Merge branch 'master' into add_limits_endpoint