Fixed a bug in ScanLibrary that caused duplicated Volumes. Implemented APIs for navigating down to Volume for webui.

This is rough code and needs to be polished and refactored.

API/Data/Migrations/20210101180935_AddedCoverImageToSeries.cs

@@ -0,0 +1,23 @@
+using Microsoft.EntityFrameworkCore.Migrations;
+
+namespace API.Data.Migrations
+{
+    public partial class AddedCoverImageToSeries : Migration
+    {
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.AddColumn<string>(
+                name: "CoverImage",
+                table: "Series",
+                type: "TEXT",
+                nullable: true);
+        }
+
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropColumn(
+                name: "CoverImage",
+                table: "Series");
+        }
+    }
+}