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.
did ALL THE THINGS; uniter_test passing again; loads of cleanup to do
better reboot-error handling/layering in RunCommands
Add upgrade step to put the system identity back.

Conflicts:
	upgrades/upgrade_test.go
missing import.
all: move MachineJob decl to state/multiwatcher
tests pass
cleanups
Setting default network bridge name on config creation.
Rename parseTag to tagToCollectionAndId
Update tests too
fix test not running
Review fix.
Style Guide Edit

Add "one space after period" to style guide.
Merge pull request #1197 from johnweldon/0-parseTag-refactor

Rename `parseTag` to `tagToCollectionAndId` for clarity

Minor feedback from previous PR - mechanical change

(Review request: http://reviews.vapour.ws/r/508/)