refactoring module yum

pas mal de modif...
l'idée est d'éclater en classes distinctes les repos yum

Egalement : Utilisation de hiera pour surcharger les url

Ex:hieradata/production/modules/yum.yaml
yum::custom::repo_custom_noarch: 'http://192.168.184.1/packages/custom/el$releasever/noarch/'
yum::custom::repo_custom_arch:   'http://192.168.184.1/packages/custom/el$releasever/$basearch/'

yum::kermit::repo_kermit_custom:    'http://192.168.184.1/packages/kermit-custom/el$releasever/$basearch/'
yum::kermit::repo_kermit_thirdpart: 'http://192.168.184.1/packages/kermit-thirdpart/el$releasever/$basearch/'

yum::sensu::repo_sensu: 'http://192.168.184.1/packages/sensu/el/$releasever/$basearch/'