add yosemite to macOSXSeries
Move backupsMetaC into backups.go.
Move state/backups.go to state/backups/storage.go.
Use the common implementation for getting a new State.
Add a note about dropping the corresponding function in state.
Use *state.State rather than the temp surrogate interfaces.
Fix a couple storage names.
Gut the backup plugin, but keep it around for backward-compatibility.
Use the old plugin code for 1.20.
Add a deprecation warning message.
Add a TODO comment about removing the plugin.
Improve the visibility of the divider comment.
Skip new backups for 1.21 as well.
Add yosemite
Extract common method for fetching network interface id for instance
Skeleton implementation of ReleaseAddress
Skeleton (failing) test
Fix a missed change.
Merge pull request #1182 from ericsnowcurrently/backups-storage-go

Move state/backups.go to the state/backups/storage.go.

This eliminates the state/backups dependency in state.  See https://bugs.launchpad.net/juju-core/+bug/1392520.

(Review request: http://reviews.vapour.ws/r/493/)
Add upgrade step to put the system identity back.

Conflicts:
	upgrades/upgrade_test.go