better code to handle all these events

file transfer request can now be stored in awaiting_events queue and recalled from roster / filetransfer / popup notification

single messages are well handled: they are saved in awaiting_events if needed and are printed when we dubble click a contact row, or systray or popup window

it now contains subject of messages

refactor connect so that new_account can use it (SSL and SRV now works when we create a new account)

comments never hurt; fix DeprecationWarning on passing float to scale_simple; do not show bigger avatar if avatar is not bigger