Folder Watching (#1467)

* Hooked in a server setting to enable/disable folder watching

* Validated the file rename change event

* Validated delete file works

* Tweaked some logic to determine if a change occurs on a folder or a file.

* Added a note for an upcoming branch

* Some minor changes in the loop that just shift where code runs.

* Implemented ScanFolder api

* Ensure we restart watchers when we modify a library folder.

* Fixed a unit test

API/Entities/Enums/ServerSettingKey.cs

@@ -91,5 +91,10 @@ namespace API.Entities.Enums
         /// </summary>
         [Description("TotalBackups")]
         TotalBackups = 16,
+        /// <summary>
+        /// If Kavita should watch the library folders and process changes
+        /// </summary>
+        [Description("EnableFolderWatching")]
+        EnableFolderWatching = 17,
     }
 }