Introduce Parse{Unit,Service,Machine}
Merge branch 'master' of https://github.com/juju/juju into 106-parsetag-refactor

Conflicts:
	state/api/deployer/unit.go
	state/api/firewaller/service.go
	state/api/provisioner/machine.go
wip
Update for juju/names part 3
Final tweak
update to latest juju/names
Merge branch 'master' of https://github.com/juju/juju into 106-parsetag-refactor
fixups after merge from trunk
Merge pull request #103 from davecheney/106-parsetag-refactor

Update for juju/names refactor part 3

* Replace all the calls to ParseTag(tag, hint) to a specific ParseXXXTag method. 
* Where ParseTag is not called with a hint, adjust as necessary, there is one call for this in the codebase.
* Add some grossness where code like

type Unit struct { tag string }
func (u *Unit) Name() { _, id, err := names.ParseTag(tag, names.UnitTagKind); if err != nil { panic(err) } }

Into something a little more explicit using type specific ParseXXXTag methods.

In the next branch rather than storing the string form of the tag inside the Unit structure (without validation I may add), then parsing it (and possibly panicing) to get its Id, store a real Tag value in the struct then calls to name can just return the Id of the tag (or a more specific value available on the Tag's implementation type).