fixes #4599 - DNS and DHCP records for BMC and managed interfaces not using FQDN
fixes #4381: dns records are being update after changes to host when dhcp is also present
fixes #4123 - libvirt imaging support using backing volumes
fixes #2739 - add ActiveSupport::Concern syntax to mixins
fixes #2411 - move files in /models to /concerns, /services, /mailers, /observers