Use utils/featureflags.
Update juju/utils to get feature flags.
Be more explicit.
Remove unneeded imports.
Merge branch 'master' into feature-flags
Fix the imports... always the imports.
Merge pull request #1221 from howbazaar/feature-flags

Implement feature flags for Juju

Proposal for a feature flag implementation in Juju.

Flags are specified in the environment.  Once an environment is bootstrapped with a particular feature flag set, it cannot be changed.  All agents started in that environment will  have the same feature flag set.

NOTE: windows isn't done yet as I haven't figured out how.

(Review request: http://reviews.vapour.ws/r/531/)