Auto-Organize: Async operation and instant feedback UI (reworked)

This commit includes changes to enable and stabilize asyncronous
operation in the auto-organize area. Here are the key points:

- The auto-organize correction dialog is now closed (almost) instantly.
This means that the user does not have to wait until the file copy/move
operation is completed in order to continue. (even with local HDs the
copy/move process can take several minutes or even much longer with
network destination).
- This commit also implements locking of files to be organized in order
to prevent parallel processing of the same item. In effect, there can be
2 or more manual organization operations active even while the normal
auto-organization task is running without causing any problems
- The items that are currently being processed are indicated as such in
the log with an orange color and a spinner graphic
- The client display is refreshed through websocket messages
- A side effect of this is that other clients showing the auto-organize
log at the same time are always up-to-date as well

MediaBrowser.WebDashboard/MediaBrowser.WebDashboard.csproj

@@ -182,6 +182,9 @@
     <Content Include="dashboard-ui\components\tvproviders\xmltv.template.html">
       <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
     </Content>
+    <Content Include="dashboard-ui\css\images\throbber.gif">
+      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+    </Content>
     <Content Include="dashboard-ui\scripts\userpasswordpage.js">
       <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
     </Content>