Fixes #2314 - fine grain for RAM selectors

Fixes #16358 - Load dashboard on puppet proxy view

Some changes made to the main dashboard caused the puppet dashboard on
the smart proxy page to break.
This commit also includes small improvements to the dashboard loading
performance.

Fixes #16318 - PXE templates now work in safemode (#3783)

pxe_kernel_options added to safemode

Fixes #7806 - allow taxonomy association on role level

refs #1170 - capitalize statistics heading (#3780)

fixes #1170 - adds additional charts to statistics page

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

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 #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.

Fixes #16238 - Speed up dashboard loading time.

I've change report host to inner query and used a join, in
my testing, this speed up dramaticilly dashboard loading
time, on my setup from 60 seconds to under 10 seconds.

fixes #16172 - remove base_class override in template subclasses

On Rails 5.0, the base_class is used during model instantiation to
validate STI relationships as it now casts similarly to Foreman::STI,
causing failures when base_class returns the subclass rather than parent...