Change namespace for defaults controllers

To allow proper path prefix for view partials when using
config.action_view.prefix_partial_path_with_controller_namespace

app/controllers/default/units_controller.rb

@@ -0,0 +1,11 @@
+class Default::UnitsController < ApplicationController
+  navigation_tab :units
+
+  before_action except: :index do
+    raise AccessForbidden unless current_user.at_least(:admin)
+  end
+
+  def index
+    @units = current_user.units.defaults_diff
+  end
+end