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/LogCacheService.cs

@@ -0,0 +1,50 @@
+using Jackett.Models;
+using NLog;
+using NLog.Targets;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+using Jackett.Services.Interfaces;
+
+namespace Jackett.Services
+{
+
+    [Target("LogService")]
+    public class LogCacheService: TargetWithLayout, ILogCacheService
+    {
+        private static List<CachedLog> logs = new List<CachedLog>();
+
+        public void AddLog(LogEventInfo l)
+        {
+            lock (logs)
+            {
+                logs.Insert(0, new CachedLog()
+                {
+                    Level = l.Level.Name,
+                    Message = l.Message,
+                    When = l.TimeStamp 
+                });
+                logs = logs.Take(50).ToList();
+            }
+
+        }
+
+        public List<CachedLog> Logs
+        {
+            get
+            {
+                lock (logs)
+                {
+                    return logs.ToList();
+                }
+            }
+        }
+
+        protected override void Write(LogEventInfo logEvent)
+        {
+            AddLog(logEvent);
+        }
+    }
+}