Changed plugins to abstract classes

src/Artemis.Storage/Migrations/20190415185618_SettingsPluginGuid.cs

@@ -0,0 +1,33 @@
+using System;
+using Microsoft.EntityFrameworkCore.Migrations;
+
+namespace Artemis.Storage.Migrations
+{
+    public partial class SettingsPluginGuid : Migration
+    {
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.AddColumn<Guid>(
+                name: "PluginGuid",
+                table: "Settings",
+                nullable: false,
+                defaultValue: new Guid("00000000-0000-0000-0000-000000000000"));
+
+            migrationBuilder.CreateIndex(
+                name: "IX_Settings_Name_PluginGuid",
+                table: "Settings",
+                columns: new[] { "Name", "PluginGuid" });
+        }
+
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropIndex(
+                name: "IX_Settings_Name_PluginGuid",
+                table: "Settings");
+
+            migrationBuilder.DropColumn(
+                name: "PluginGuid",
+                table: "Settings");
+        }
+    }
+}