display community news in simple window; check timestamp and serial number * news-dock-widget.cc, news-dock-widget.h: Delete. * libgui/src/module.mk: Update file lists. * main-window.h, main-window.cc (news_reader): Move here from news-dock-widget.h and news-dock-widget.cc. Store page serial number. (news_reader::process): Check serial number. Save timestamp and serial number to settings file. (main_window::community_news_window): New data member. (main_window::main_window): Initialize it. Maybe display community news. (main_window::~main_window): Delete community_news_window. (fixed_community_news): New static constant. (main_window::load_and_display_community_news): New slot. (main_window::display_community_news): New slot. (main_window::news_window): Delete member variable and all uses.