Mostly backend models stuff

Changed some models, did some work on database, created a class diagram.

KTUSAPS.Data/Model/PublishedFeedback.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Collections.Generic;
 using System.ComponentModel.DataAnnotations;
+using System.ComponentModel.DataAnnotations.Schema;
 using System.Linq;
 using System.Text;
 using System.Threading.Tasks;
@@ -9,6 +10,7 @@ namespace KTUSAPS.Data.Model
 {
     public class PublishedFeedback
     {
+        [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
         public int Id { get; set; }
         [Required]
         [MaxLength]