New Identity NG Panels missing stuff in settings.py/rst

Newly added NG panels are missing some definitions
in settings.py and settings.rst

NG Domains default is not defined in settings.py
https://review.openstack.org/#/c/387771/

NG Roles default should be described in settings.rst
documentation
https://review.openstack.org/#/c/222825/

Change-Id: I0bddbf2c829467c2c1ea20d96124c66ec46c50b4

doc/source/topics/settings.rst

@@ -439,6 +439,7 @@ Default::
     'images_panel': True,
     'flavors_panel': False,
     'users_panel': False,
+    'roles_panel': False,
     'domains_panel': False
   }
 

openstack_dashboard/settings.py

@@ -316,7 +316,8 @@ ANGULAR_FEATURES = {
     'images_panel': True,
     'flavors_panel': False,
     'users_panel': False,
-    'roles_panel': False
+    'roles_panel': False,
+    'domains_panel': False
 }
 
 # Notice all customizable configurations should be above this line