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.Server.Implementations/MediaBrowser.Server.Implementations.csproj

@@ -149,6 +149,7 @@
     <Compile Include="EntryPoints\UsageReporter.cs" />
     <Compile Include="FileOrganization\EpisodeFileOrganizer.cs" />
     <Compile Include="FileOrganization\Extensions.cs" />
+    <Compile Include="FileOrganization\FileOrganizationNotifier.cs" />
     <Compile Include="FileOrganization\FileOrganizationService.cs" />
     <Compile Include="FileOrganization\NameUtils.cs" />
     <Compile Include="FileOrganization\TvFolderOrganizer.cs" />