Merge branch 'hotfix/TrackingEventViewModel-typing' into master

Fixes a bug inadvertently introduced when converting `List<T>` to `Collection<T>` (f8f5ed3); one instance of this was missed in the (pre-release) GoldSim courseware site. Whoops!

Author: JeremyCaney

Views/Shared/_TrackEvents.cshtml

@@ -1,4 +1,4 @@
-@model List<TrackingEventViewModel>
+@model Collection<TrackingEventViewModel>
 
 <script>
   @foreach (var trackingEvent in Model) {
@@ -14,6 +14,6 @@
 </script>
 
 <!--
-  Content Type: List<TrackingEventViewModel>
+  Content Type: Collection<TrackingEventViewModel>
   View Location: ~/Views/Shared/_TrackEvents.cshtml
 -->

_ViewImports.cshtml

@@ -11,6 +11,7 @@
 @using Microsoft.AspNetCore.Html
 @using Microsoft.AspNetCore.Mvc.Razor
 @using System.Web
+@using System.Collections.ObjectModel
 
 @addTagHelper *, Microsoft.AspNetCore.Mvc.TagHelpers
 @addTagHelper *, GoldSim.Web