Changing BotBase behaviour to fluent api

- removing unecessary constructors from BotBase
- removing generics from BotBase
- removing generics from SessionBase
- adding StartFormFactory interface
- adding DefaultStartFormFactory
- adding multiple methods to BotBaseBuilder

TelegramBotBase/Factories/DefaultStartFormFactory.cs

@@ -0,0 +1,26 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+using TelegramBotBase.Form;
+
+namespace TelegramBotBase.Factories
+{
+    public class DefaultStartFormFactory : Interfaces.IStartFormFactory
+    {
+        private readonly Type _startFormClass;
+
+        public DefaultStartFormFactory(Type startFormClass)
+        {
+            if (!typeof(FormBase).IsAssignableFrom(startFormClass))
+                throw new ArgumentException("startFormClass argument must be a FormBase type");
+
+            _startFormClass = startFormClass;
+        }
+
+
+        public FormBase CreateForm()
+        {
+            return _startFormClass.GetConstructor(new Type[] { })?.Invoke(new object[] { }) as FormBase;
+        }
+    }
+}