provider/maas: verify credentials early in bootstrap

Verify credentials early in the bootstrap process by
issuing a query to MAAS and checking the status code
on the response (i.e. check if it's 401). Provide a
user-friendly error message, and log the underlying
error at debug level.

Partially fixes https://bugs.launchpad.net/juju-core/+bug/1362072
Fix import grouping
Merge pull request #865 from axw/lp1362072-provider-verify-credentials-maas

provider/maas: verify credentials early in bootstrap

Verify credentials early in the bootstrap process by
issuing a query to MAAS and checking the status code
on the response (i.e. check if it's 401). Provide a
user-friendly error message, and log the underlying
error at debug level.

Partially fixes https://bugs.launchpad.net/juju-core/+bug/1362072
action-fail: a jujuc command for Actions to set an error state

action-fail permits an Action to set an error value which will be returned to
the stateserver upon completion of the Action.  This does not prevent
action-set from adding more values to the results map.
action-fail: a jujuc command for Actions to set an error state

action-fail now uses the ActionFinish endpoint on State, so that any
values set in the action's result map will be handed back even in the
case of a failed Action.  The final call to action-fail will be the
message which is handed back along with the fail status.
action-fail: a jujuc command for Actions to set an error state

Final refactor of action-fail for action-set and actionFinish.
Merge pull request #868 from binary132/action-fail

jujuc action-fail

This is a re-open of https://github.com/juju/juju/pull/520 as the lander failed to see the script invocation.
Action / ActionResult EnvUUID and related changes
Merge pull request #860 from johnweldon/env-uuid-actions

Prepend environment UUID to Action and ActionResult document _id's

Also normalize Action and ActionResult methods to more closely resemble other entity use of methods like `Name()`, etc.
Meter status made available to the uniter. The meter status is set on state and exposed to the charm
hooks in the form of environment variables. In addition, a new hook, meter-status-changed is executed
every time the meter status for that unit changes.
Merge pull request #817 from tasdomas/meter_status

Meter status

Meter status information available as hook context environment variables.

Meter status information will be set per-unit, once the metrics pipeline is in place.
5 minutes. This change is then detected by the uniter watcher and the collect-metrics hook is executed.

collect-metrics hook execution triggered by uniter. The uniter signals the collect-metrics hook to be executed every 5 minutes.