tweaks to make Uniter easier
tweaks to make Uniter easier

* added hook.Kind.IsRelation()
* made hook.StateFile.Read return a State, not a *State

R=niemeyer
CC=
https://codereview.appspot.com/6454169

frankban/juju-tmp,mattyw/juju,mikemccracken/juju,dooferlad/juju,tasdomas/juju,bac/juju,mjs/juju,davecheney/juju,marcoceppi/juju,Altoros/juju-cloudsigma,frankban/juju,tsakas/juju,AdamIsrael/juju,cloud-green/juju,cherylj/juju,dimitern/juju,ericsnowcurrently/juju,rogpeppe/juju,alesstimec/juju,voidspace/juju,waigani/juju,tsakas/juju,alesstimec/juju,mhilton/juju-juju,mikemccracken/juju,Altoros/juju-vmware,waigani/juju,perrito666/juju,axw/juju,bac/juju,mjs/juju,mattyw/juju,frankban/juju-tmp,dimitern/juju,gabriel-samfira/juju,fwereade/juju,jrwren/juju,gabriel-samfira/juju,macgreagoir/juju,cmars/juju,makyo/juju,macgreagoir/juju,marcoceppi/juju,bz2/juju,axw/juju,gabriel-samfira/juju,Altoros/juju-vmware,marcoceppi/juju,rogpeppe/juju,mjs/juju,thomnico/juju,sinzui/juju,tasdomas/juju,cherylj/juju,AdamIsrael/juju,sinzui/juju,marcmolla/juju,Altoros/juju-cloudsigma,dooferlad/juju,reedobrien/juju,marcmolla/juju,fwereade/juju,wwitzel3/juju,dooferlad/juju,mikemccracken/juju,dooferlad/juju,mhilton/juju,howbazaar/juju,ericsnowcurrently/juju,kat-co/juju,mhilton/juju-juju,perrito666/juju,perrito666/juju,waigani/juju,fwereade/juju,reedobrien/juju,voidspace/juju,Altoros/juju-vmware,perrito666/juju,mjs/juju,frankban/juju,tsakas/juju,cmars/juju,dimitern/juju,kat-co/juju,jrwren/juju,bz2/juju,tych0/juju,alesstimec/juju,mhilton/juju-juju,axw/juju,tych0/juju,thomnico/juju,davecheney/juju,tasdomas/juju,mikemccracken/juju,frobware/juju,Altoros/juju-cloudsigma,reedobrien/juju,voidspace/juju,makyo/juju,frankban/juju,marcmolla/juju,frankban/juju,anastasiamac/juju,anastasiamac/juju,anastasiamac/juju,mjs/juju,wwitzel3/juju,mhilton/juju-juju,cmars/juju,mhilton/juju,wwitzel3/juju,marcoceppi/juju,tych0/juju,davecheney/juju,howbazaar/juju,tych0/juju,bogdanteleaga/juju,bz2/juju,bac/juju,wwitzel3/juju,kat-co/juju,cloud-green/juju,bogdanteleaga/juju,mhilton/juju,jrwren/juju,sinzui/juju,frankban/juju-tmp,rogpeppe/juju,gabriel-samfira/juju,alesstimec/juju,cloud-green/juju,Altoros/juju-cloudsigma,frobware/juju,mjs/juju,kat-co/juju,ericsnowcurrently/juju,tasdomas/juju,mjs/juju,voidspace/juju,macgreagoir/juju,waigani/juju,cmars/juju,dimitern/juju,thomnico/juju,mikemccracken/juju,howbazaar/juju,ericsnowcurrently/juju,bac/juju,axw/juju,cherylj/juju,marcmolla/juju,perrito666/juju,dimitern/juju,bz2/juju,bogdanteleaga/juju,bogdanteleaga/juju,Altoros/juju-vmware,cherylj/juju,reedobrien/store,sinzui/juju,reedobrien/juju,mattyw/juju,frankban/juju-tmp,makyo/juju,frankban/juju,frobware/juju,AdamIsrael/juju,anastasiamac/juju,mhilton/juju,marcmolla/juju,howbazaar/juju,davecheney/juju,cloud-green/juju,ericsnowcurrently/juju,bac/juju,dooferlad/juju,bz2/juju,macgreagoir/juju,gabriel-samfira/juju,alesstimec/juju,axw/juju,fwereade/juju,tsakas/juju,mattyw/juju,thomnico/juju,kat-co/juju,howbazaar/juju,AdamIsrael/juju,reedobrien/juju,macgreagoir/juju,makyo/juju,anastasiamac/juju