fixes #1170 - adds additional charts to statistics page

this patch adds: hostgroups, compute resources, location
and organizations if they are enabled.

refs #12634 - remove blank i18n string, match capitalisation

refs #12544 - replace ordered interpolation with named variables

Fixes #12634 - New HW Model flag pxe_loader

Implementation of

https://github.com/theforeman/rfcs/blob/master/text/0001-PXE-Booting-UEFI.md

In short, new host/hostgroup flag PXE loader is added to specify TFTP
DHCP filename and Foreman now orchestrates all PXE-capable templates...

Fixes #12544 - added errors from host to cancelBuild
Now the flash will contain detailed error messages.

Fixes #15814 - Reset override params when override is off

Fixes #16044 - Load dashboard widgets via ajax

This speeds up dasboard loading as widgets are loaded in the background
and do not block rendering, as well as allow the dashboard to load
correctly even if some of the widgets are broken.

templates - sync from community-templates

i18n - extracting new, pulling from tx

fixes #16243 - make Host::Managed.new's options arg optional

The options argument no longer exists on Rails 5 as it was part of the
support for protected_attrs. The argument list to .new should be handled
more defensively, like Host::Base.