rebar_core: fix consistency issues caused by 252b31f
rebar_core: fix consistency issues caused by 252b31f

- refactor plugin dirs code to be simpler and easier to read
- use erlang-mode's default (%%) comments for portability/consistency
- make sure erlang-mode's indenter is used so that a future whole
  buffer indent doesn't get messed up

norton/rebar,jacktang/rebar,lrascao/rebar,matwey/rebar,evnix/rebar,surik/rebar3,processone/rebar3,K2InformaticsGmbH/rebar,choptastic/rebar,scatterbrain/rebar,lrascao/rebar,benoitc/rebar3,tsloughter/rebar3,linearregression/rebar3,norton/rebar3,RubberCthulhu/rebar,beni55/rebar,jbalint/rebar3,matwey/rebar,rebar/rebar,vladdu/rebar3,deadok22/rebar,basho/rebar,rebar/rebar3,CMoH/rebar,macintux/rebar,fabiankrol/rebar3,bsmr-erlang/rebar,lrascao/rebar3,evnix/rebar,jacktang/rebar,fauxsoup/rebar3,apache/couchdb-rebar,blt/rebar3,K2InformaticsGmbH/rebar,zugolosian/rebar3,bsmr-erlang/rebar,basho/rebar,csyangchen/rebar,heroku/rebar,paulo-ferraz-oliveira/rebar,beni55/rebar-1,CMoH/rebar,macintux/rebar,K2InformaticsGmbH/rebar,lrascao/rebar,blt/rebar3,GabrielNicolasAvellaneda/rebar,dcarastan/rebar,syl20bnr/rebar,choptastic/rebar,beni55/rebar,rebar/rebar,lpgauth/rebar,project-fifo/rebar3,CMoH/rebar,fabiankrol/rebar3,syl20bnr/rebar,project-fifo/rebar3,shkumagai/rebar,wcy123/rebar,macintux/rebar,kellymclaughlin/rebar3,SiDen/rebar,RubberCthulhu/rebar,rebar/rebar,csyangchen/rebar,oubiwann/rebar,sile/rebar3,fishcakez/rebar3,lrascao/rebar,erlang/rebar3,beni55/rebar,matwey/rebar,deadok22/rebar,paulo-ferraz-oliveira/rebar,platinumthinker/rebar,processone/rebar3,walrusVision/rebar3,linearregression/rebar3,bsmr-erlang/rebar,syl20bnr/rebar,evnix/rebar,matwey/rebar,scatterbrain/rebar,csyangchen/rebar,cloudant/couchdb-rebar,zugolosian/rebar3,beni55/rebar-1,SiDen/rebar,apache/couchdb-rebar,fauxsoup/rebar3,matwey/rebar,lrascao/rebar,norton/rebar,K2InformaticsGmbH/rebar,choptastic/rebar,sile/rebar3,djnym/rebar3,cloudant/couchdb-rebar,dcarastan/rebar,surik/rebar3,bsmr-erlang/rebar,dcarastan/rebar,norton/rebar,GabrielNicolasAvellaneda/rebar,ferd/rebar3,cloudant/couchdb-rebar,platinumthinker/rebar,paulo-ferraz-oliveira/rebar,oubiwann/rebar,apache/couchdb-rebar,norton/rebar,jacktang/rebar,lpgauth/rebar,oubiwann/rebar,rebar/rebar3,saleyn/rebar3,lpgauth/rebar,GabrielNicolasAvellaneda/rebar,scatterbrain/rebar,shkumagai/rebar,benoitc/rebar3,heroku/rebar,jbalint/rebar3,platinumthinker/rebar,SiDen/rebar,walrusVision/rebar3,K2InformaticsGmbH/rebar,wcy123/rebar,shkumagai/rebar