Remove history_item and layout from pch.

Also move some code to separate modules.
Also create history item views by Window::Controller.

Telegram/SourceFiles/data/data_session.h

@@ -10,6 +10,8 @@ https://github.com/telegramdesktop/tdesktop/blob/master/LEGAL
 #include "chat_helpers/stickers.h"
 #include "dialogs/dialogs_key.h"
 
+struct HistoryMessageGroup;
+
 namespace Data {
 
 class Feed;