fix: added missing properties for submitted form.

Author: dimitriadamou

FormitizeAPI/API/Response/SubmittedFormGetEntry.cs

@@ -172,5 +172,47 @@ public Dictionary<string, SubmittedFormAttachments> Attachments
             get; set;
         }
 
+        [JsonProperty(PropertyName = "dateSubmitted")]
+        public int DateSubmittedUnixTimestamp
+        {
+            get; private set;
+        }
+
+        public DateTime DateSubmitted
+        {
+            get
+            {
+                return new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc).AddSeconds(DateSubmittedUnixTimestamp);
+            }
+        }
+
+        [JsonProperty(PropertyName = "dateModified")]
+        public int DateModifiedUnixTimestamp
+        {
+            get; private set;
+        }
+
+        public DateTime DateModified
+        {
+            get
+            {
+                return new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc).AddSeconds(DateModifiedUnixTimestamp);
+            }
+        }
+
+        [JsonProperty(PropertyName = "dateCreated")]
+        public int DateCreatedUnixTimestamp
+        {
+            get; private set;
+        }
+
+        public DateTime DateCreated
+        {
+            get
+            {
+                return new DateTime(1970, 1, 1, 0, 0, 0, DateTimeKind.Utc).AddSeconds(DateCreatedUnixTimestamp);
+            }
+        }
+
     }
 }