Changes for viewing built-in tabs in studio

Changed "Status Page" -> "Page".

UX:
    support for displaying built-in tabs
    restored drag and drop on Studio Pages
    additional styling for fixed state on Studio Pages
    add a new page action added to bottom of Studio Pages

Dev
    changes for viewing tabs in studio,
    refactored the tab code,
    decoupled the code from django layer.
    is_hideable flag on tabs
    get_discussion method is needed to continue to support
external_discussion links for now since used by 6.00x course.
    override the __eq__ operator to support comparing with
dict-type tabs.

Test
    moved test code to common,
    added acceptance test for built-in pages
    added additional unit tests for tabs.
    changed test_split_modulestore test to support serializing objects
that are fields in a Course.

Env:
    updated environment configuration settings so they are
    consistent for both cms and lms.

cms/static/coffee/src/views/tabs.coffee

@@ -17,6 +17,7 @@ define ["jquery", "jquery.ui", "backbone", "js/views/feedback_prompt", "js/views
       )
 
       @options.mast.find('.new-tab').on('click', @addNewTab)
+      $('.add-pages .new-tab').on('click', @addNewTab)
       @$('.components').sortable(
         handle: '.drag-handle'
         update: @tabMoved
@@ -34,7 +35,7 @@ define ["jquery", "jquery.ui", "backbone", "js/views/feedback_prompt", "js/views
           tabs.push($(element).data('locator'))
       )
 
-      analytics.track "Reordered Static Pages",
+      analytics.track "Reordered Pages",
         course: course_location_analytics
 
       saving = new NotificationView.Mini({title: gettext("Saving…")})
@@ -68,7 +69,7 @@ define ["jquery", "jquery.ui", "backbone", "js/views/feedback_prompt", "js/views
         {category: 'static_tab'}
       )
 
-      analytics.track "Added Static Page",
+      analytics.track "Added Page",
         course: course_location_analytics
 
     deleteTab: (event) =>
@@ -82,7 +83,7 @@ define ["jquery", "jquery.ui", "backbone", "js/views/feedback_prompt", "js/views
               view.hide()
               $component = $(event.currentTarget).parents('.component')
 
-              analytics.track "Deleted Static Page",
+              analytics.track "Deleted Page",
                 course: course_location_analytics
                 id: $component.data('locator')
               deleting = new NotificationView.Mini