Take a tag not a string
firewaller.Unit takes names.Tag
firewaller.Machine takes names.Tag
firewaller.Machine takes names.Tag
more string -> Tag conversions
Move string -> Tag conversions.
More string -> names.Tag work
Merge branch 'master' of https://github.com/juju/juju into 114-state-accessors-take-tags
Merge branch '115-state-string-tags' into 114-state-accessors-take-tags
Use concrete types rather than names.Tag interface
fix todo
Merge branch 'master' of https://github.com/juju/juju into 114-state-accessors-take-tags

Conflicts:
	state/apiserver/login_test.go
	worker/provisioner/container_initialisation_test.go
Small post merge tweak
Merge branch 'master' of https://github.com/juju/juju into 114-state-accessors-take-tags
fix merge issue
Merge pull request #156 from davecheney/114-state-accessors-take-tags

More string -> names.Tag conversion