[jim++] use message text if user does not give message title. message == preset message [in prefs window]

show gajim.png image instead of STOCK_APPLY image cause in many theme (gnome one) it's too small and it looks ugly

pychecker on our files. everyone please have a look so we do not do the same mistakes and in case you catch a mistake I did when cleaning

TODO: fill animated folder with his emoticons file

commit first part of special notifications (aka buddy pounces). at last make Choose Sound dlg a class; TODO: actually write to config user settings as well as take those into account [jim++]

preferences window is created on the fly like every other window (well apart from FT [TODO for that]); this is good as we do not want such window to sit in memory; also fix some border width and spacing in prefs window

nes DataForm design that allow each widget on each line to have different size (it means I remove the gtk.Table). Fixes #1633