Feature/netcore preparation (#2072)

* Use platform detection that works on mono 4.6+

* Move to use package reference for restoring nuget packages.

* DateTimeRoutines does not have Nuget packages that support .NET Standard (and therefore .NET Core). We will have to include them for now until we can get rid of this dependency.

* Start spliting some interfaces into their own files - this will help by allowing us to split them out in the future into a seperate project so the actual implementations can stay within their respective architectures when required

* Move out common libraries

* Few more tidy up tasks to get things working with .NET Standard

* Restructure the solution layout

* Encoding work to reduce rework later on platforms without Windows codepages (or require compliance with RFC1345)

* Move folder structure around to have more natural layout of the solutions

* DI server configuration to get rid of "temporary" hack and dependency circle for serverservice

* Make all encoding consistent to match the expected encoding casing for earlier versions of mono.

src/Jackett.Common/Services/Interfaces/IIndexerManagerService.cs

@@ -0,0 +1,18 @@
+using Jackett.Indexers;
+using System.Collections.Generic;
+using System.Threading.Tasks;
+
+namespace Jackett.Services.Interfaces
+{
+    public interface IIndexerManagerService
+    {
+        Task TestIndexer(string name);
+        void DeleteIndexer(string name);
+        IIndexer GetIndexer(string name);
+        IWebIndexer GetWebIndexer(string name);
+        IEnumerable<IIndexer> GetAllIndexers();
+
+        void InitIndexers(IEnumerable<string> path);
+        void InitAggregateIndexer();
+    }
+}