add close button [no new string here, thanks to GTK+] and show it for when we...

add close button [no new string here, thanks to GTK+] and show it for when we read received single messages instead of showing cancel [which is when we send]; add icon to send button; move ui preparation code to the right method and add some code to handle show/hide for close/cancel button. add a fixme for after 0.9 for string thing