Check if attachment is an image before showing the thumbnail
first pass at autoloading core classes
move remaining connection type classes to separate files

this should fix errors related to lazy loading
rename $args to $render_args
remove extract() usage in _p2p_get_list()
remove extract() from p2p_get_connections()
remove extract() from P2P_List::render()
remove extract() from _p2p_get_connections()
remove extract() from p2p_create_direction()
avoid variable variables in P2P_Connection_Type::get_desc()