Pull modal cover and date utils into their own files.

Move overview-specific functions into overview.js.

cms/static/coffee/src/views/module_edit.coffee

@@ -1,7 +1,7 @@
 define ["backbone", "jquery", "underscore", "gettext", "xblock/runtime.v1",
         "js/views/feedback_notification", "js/views/metadata", "js/collections/metadata"
-        "jquery.inputnumber", "xmodule"],
-(Backbone, $, _, gettext, XBlock, NotificationView, MetadataView, MetadataCollection) ->
+        "js/utils/modal", "jquery.inputnumber", "xmodule"],
+(Backbone, $, _, gettext, XBlock, NotificationView, MetadataView, MetadataCollection, ModalUtils) ->
   class ModuleEdit extends Backbone.View
     tagName: 'li'
     className: 'component'
@@ -87,7 +87,7 @@ define ["backbone", "jquery", "underscore", "gettext", "xblock/runtime.v1",
         id: _this.model.id
 
       data.metadata = _.extend(data.metadata || {}, @changedMetadata())
-      @hideModal()
+      ModalUtils.hideModalCover()
       saving = new NotificationView.Mini
         title: gettext('Saving…')
       saving.show()
@@ -102,17 +102,12 @@ define ["backbone", "jquery", "underscore", "gettext", "xblock/runtime.v1",
       event.preventDefault()
       @$el.removeClass('editing')
       @$component_editor().slideUp(150)
-      @hideModal()
-
-    hideModal: ->
-      $modalCover = $(".modal-cover")
-      $modalCover.hide()
-      $modalCover.removeClass('is-fixed')
+      ModalUtils.hideModalCover()
 
     clickEditButton: (event) ->
       event.preventDefault()
       @$el.addClass('editing')
-      $(".modal-cover").show().addClass('is-fixed')
+      ModalUtils.showModalCover(true)
       @$component_editor().slideDown(150)
       @loadEdit()