Add new container page that can display nested xblocks

This is the changes for STUD-1244, which introduces the ability for Studio to display
arbitrarily nested xblocks. In this change, a new container page is introduced which can
display nested xblocks. In particular, the xblock type of 'vertical' is special cased
to be shown inline as a collapsible section. The unit page is mostly unchanged, except
that container xblock's are shown as a link to their container page, rather than being
shown inline.

cms/templates/unit.html

@@ -11,7 +11,8 @@ from xmodule.modulestore.django import loc_mapper
 
 <%block name="jsextra">
   <script type='text/javascript'>
-require(["domReady!", "jquery", "js/models/module_info", "coffee/src/views/unit", "jquery.ui"],
+require(["domReady!", "jquery", "js/models/module_info", "coffee/src/views/unit", "jquery.ui",
+        "xmodule", "coffee/src/main", "xblock/cms.runtime.v1"],
     function(doc, $, ModuleModel, UnitEditView, ui) {
   window.unit_location_analytics = '${unit_locator}';
 
@@ -20,6 +21,7 @@ require(["domReady!", "jquery", "js/models/module_info", "coffee/src/views/unit"
 
   new UnitEditView({
     el: $('.main-wrapper'),
+    view: 'unit',
     model: new ModuleModel({
       id: '${unit_locator}',
       state: '${unit_state}'
@@ -53,7 +55,7 @@ require(["domReady!", "jquery", "js/models/module_info", "coffee/src/views/unit"
         <article class="unit-body window">
         <p class="unit-name-input"><label for="unit-display-name-input">${_("Display Name:")}</label><input type="text" value="${unit.display_name_with_default | h}" id="unit-display-name-input" class="unit-display-name-input" /></p>
           <ol class="components">
-            % for locator in components:
+            % for locator in locators:
             <li class="component" data-locator="${locator}"/>
             % endfor
             <li class="new-component-item adding">