fixes #18681 - moves polymorphic subject into notification object

also adds host build, destroyed and missing owner UI notifications

Fixes #14013 - add a setting for default owner of new hosts

Fixes #16982 - Scope properly when no taxonomies are set

The default scope for hosts and other objects did not restrict
properly by taxonomies. An user without organizations or
locations, could do anything it's permissions allow to.
The list of hosts was unrestricted and showed hosts in...

fixes #17533 - provision dhcp for bond child macs

fixes #18102 - a host cannot be backed by the same vm

fixes #18208 - replace audited-activerecord with audited (#4218)

Fixes #16752 - Extract template code from Host::Managed

Host::Managed contains a lot of code related with determining the
template that a host should have. Other Host objects such as
Host::Discovered might need that logic, without becoming a
Host::Managed....

Fixes #6952 - Set hostgroup after provisioning from pxe

After hostgroup provisioning, when the machine has registered
with foreman, it should be in the same hostgroup.
to achieve this behavier, the fact foreman_hostgroup should be
added to hostgroup provisioning template

Fixes #17680 - templates_used host helper

templates_used contains the names of all of the provisioning templates
kickstart used during a host build. This allows users to be able to
show the name of a provisioning template during PXEBoot, for example

Fixes #16740 - Access host params through macro