Rename page object to keep consistency

Also, add new elements and methods to it.

Finally, update the autoload of it to reflect the new name.

qa/qa/ee.rb

@@ -107,7 +107,7 @@ module QA
         end
 
         module Milestone
-          autoload :Index, 'qa/ee/page/project/milestone/index'
+          autoload :Show, 'qa/ee/page/project/milestone/show'
         end
 
         module Settings

qa/qa/ee/page/project/milestone/index.rb → qa/qa/ee/page/project/milestone/show.rb

@@ -5,15 +5,28 @@ module QA
     module Page
       module Project
         module Milestone
-          module Index
+          module Show
             def self.prepended(page)
               page.module_eval do
+                view 'ee/app/views/shared/milestones/_burndown.html.haml' do
+                  element :burndown_chart
+                  element :weight_button
+                end
+
                 view 'ee/app/views/shared/milestones/_weight.html.haml' do
                   element :total_issue_weight_value
                 end
               end
             end
 
+            def click_weight_button
+              click_element(:weight_button)
+            end
+
+            def burndown_chart
+              find_element(:burndown_chart)
+            end
+
             def total_issue_weight_value
               find_element(:total_issue_weight_value)
             end