v0.0.13 #4 - 修复和丰富 ICodeFirst.ConfigEntity 方法；

- 增加 FreeSql.Extensions.EFCoreModelBuilder 扩展库，现实与 EFCore 实体共存；
- 增加 FreeSql.RESTful.Demo 示例项目；

FreeSql.RESTful.Demo/Entity/Song.cs

@@ -1,10 +1,14 @@
-using System;
+using Microsoft.EntityFrameworkCore;
+using System;
 using System.Collections.Generic;
+using System.ComponentModel.DataAnnotations;
+using System.ComponentModel.DataAnnotations.Schema;
 using System.Linq;
 using System.Threading.Tasks;
 
 namespace FreeSql.RESTful.Demo.Entity {
 	public class Song {
+
 		public int Id { get; set; }
 		public string Title { get; set; }
 	}