Fixes #4608 - Added description field to role

Fixes #16624 - Make AuthSourceLDAP taxable

This allows users to set organizations/locations on AuthSourceLDAP
objects. That in itself might not be that useful, but it allows us to
follow on and assign the AuthSourceLDAP taxonomies to the users
autocreated through it.

Fixes #16633 - AuthSourceLDAP uses *_authenticators filters

Prior to this, non-admin users who were granted *_authenticators
permissions were not able to use them, as the controllers were looking
for *_auth_source_ldaps permissions instead.

Fixes #16219 - Interfaces API works with scoped view_hosts

Before this commit, parent_scope called 'merge' on a scope that may
contain conditions that do not make sense on 'resource_class'.

In this case, when a user with a filter :view_hosts and search
'hostgroup_fullname = foo' tried to view...

fixes #16512 - remove Setting#respond_to_missing?

respond_to_missing? changed how AR handles group_by calls on
collections, causing group_by to be interpreted as a scope on the model.
Rather than adding a database call to determine known setting names,
it's been removed again....

Fixes #16397 - set nested template_combo. objects to optional

Fixes #16461 - expose override in filter API

Fixes #15846 - Renamed use_puppet_default to omit in LookupValue

Fixes #16380 - Eager load hosts attributes
Since Rails 4, in order to load delegated attributes,
we need to use 'eager_load' instead of 'includes'

Fixes #16415 - Accept unwrapped hash with 'layout' attribute