Base Url Support (#642)

* Added base url config

* UI side is not working

* Working base url more

* Attempt to get UI to work with base url

* Implemented the ability to set the Base URL for the app

* Hooked in Base URL as a managed setting

* Ensure we always start with / for base url

* Removed default base href from debug builds. Cleaned up an issue with base url migration.

* Fixed an issue with our BaseURL migration

API/DTOs/Settings/ServerSettingDTO.cs

@@ -26,5 +26,9 @@
         /// Enables Authentication on the server. Defaults to true.
         /// </summary>
         public bool EnableAuthentication { get; set; }
+        /// <summary>
+        /// Base Url for the kavita. Defaults to "/". Managed in appsettings.json.Requires restart to take effect.
+        /// </summary>
+        public string BaseUrl { get; set; } = "/";
     }
 }