MAJOR CHANGE for ButtonGrids, Dynamic data sources, etc

- introducing a dynamic data source class (IDataSource)
- introducing a ButtonRow class for better managability
- replacing that List<ButtonBase> with ButtonRow object
- introducing ButtonFormDataSource with special methods for ButtonGrid controls
- updating ButtonGrid and refactoring of the Load/Action methods
- updating CheckButtonList and refactoring of the Load/Action methods
- updating TaggedButtonGrid and refactoring of the Load/Action methods
- adding example to the Test project

TelegramBotBase/Interfaces/IDataSource.cs

@@ -0,0 +1,43 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+using TelegramBotBase.Controls.Hybrid;
+
+namespace TelegramBotBase.Interfaces
+{
+    public interface IDataSource<T>
+    {
+
+        /// <summary>
+        /// Returns the amount of items within this source.
+        /// </summary>
+        /// <returns></returns>
+        int Count { get; }
+
+
+        /// <summary>
+        /// Returns the item at the specific index.
+        /// </summary>
+        /// <param name="index"></param>
+        /// <returns></returns>
+        T ItemAt(int index);
+
+
+        /// <summary>
+        /// Get all items from this source within this range.
+        /// </summary>
+        /// <param name="start"></param>
+        /// <param name="count"></param>
+        /// <returns></returns>
+        List<T> ItemRange(int start, int count);
+
+
+        /// <summary>
+        /// Gets a list of all items of this datasource.
+        /// </summary>
+        /// <returns></returns>
+        List<T> AllItems();
+
+
+    }
+}