增加对sql只返回string的支持;

修复添加表单时，如果关联的数据库已存在的bug

OpenAuth.App/Form/FormFactory.cs

@@ -0,0 +1,25 @@
+using System;
+using OpenAuth.Repository;
+using OpenAuth.Repository.Domain;
+using OpenAuth.Repository.Interface;
+
+namespace OpenAuth.App
+{
+    public class FormFactory
+    {
+        public static IForm CreateForm(Form form, IUnitWork<OpenAuthDBContext> unitWork)
+        {
+            if (form.FrmType == 0)
+            {
+                return new LeipiForm(unitWork);
+            }else if (form.FrmType == 1)
+            {
+                throw new Exception("自定义表单不需要创建数据库表");
+            }
+            else
+            {
+                return new DragForm(unitWork);
+            }
+        }
+    }
+}