alertmanager: normalize initd/confd

Move prometheus packages into main repo

Normalize prometheus packages

prometheus/alertmanager: update to 0.19.0

alertmanager: update to 0.18.0

prometheus/alertmanager: upgrade to 0.17.0

prometheus: checkpath on log files

Update prometheus, alertmanager init scripts

Normalize alertmanager package

prometheus/alertmanager: new APKBUILD