Fixed entity labels.

The entity labels in the following locations have been fixed:
 - search facet title: plural
 - details facet title: singular
 - association facet title: singular
 - breadcrumb: plural
 - adder dialog title: singular
 - deleter dialog title: plural

Some entity labels have been changed into the correct plural form.
Unused file install/ui/test/data/i18n_messages.json has been removed.

Ticket #1249
Ticket #1387

ipalib/plugins/pwpolicy.py

@@ -216,7 +216,7 @@ class pwpolicy(LDAPObject):
             ),
         )
 
-    label = _('Password Policy')
+    label = _('Password Policies')
     label_singular = _('password policy')
 
     takes_params = (