Enabled lazy load of poster images

This should make initial load of the movies page a little more
responsive for larger libraries. This can be used on any page loading
images.

MediaBrowser.WebDashboard/Api/DashboardService.cs

@@ -419,6 +419,7 @@ namespace MediaBrowser.WebDashboard.Api
                             {
                                 "scripts/all.js" + versionString,
                                 "thirdparty/jstree1.0/jquery.jstree.min.js",
+                                "thirdparty/jquery.unveil-custom.js",
                                 "https://www.gstatic.com/cv/js/sender/v1/cast_sender.js"
             };
 

MediaBrowser.WebDashboard/MediaBrowser.WebDashboard.csproj

@@ -653,6 +653,9 @@
     <Content Include="dashboard-ui\thirdparty\jquery-2.0.3.min.js">
       <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
     </Content>
+    <Content Include="dashboard-ui\thirdparty\jquery.unveil-custom.js">
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+    </Content>
     <Content Include="dashboard-ui\thirdparty\jquerymobile-1.4.2\images\ajax-loader.gif">
       <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
     </Content>