create GroupDb object to hold group information

#59

DataCenter_Windows/WindowsDataCenter/SQLiteRepository/GroupDb.cs

@@ -0,0 +1,12 @@
+using SQLite.Net.Attributes;
+
+namespace SQLiteRepository
+{
+    internal class GroupDb
+    {
+        [PrimaryKey, AutoIncrement]
+        public int GroupId { get; set; }
+        public string GroupName { get; set; }
+        public string AssignedUserCount { get; set; }
+    }
+}