Internal shell banner: allow the user to customize easily the banner message
(message=None -> no banner, message="" -> empty banner, ...)
Updated french translations
Updated french translation (continued)
Object inspector/Intro message: reduced left/right margins (otherwise, the
message panel was only ~10 characters large when the object inspector was in
a small area of the window layout).
Merge
Add a new calltip widget (taken from the IPython project)

- This widget has the advantage of being based on QLabel instead of QToolTip,
which makes it easier to control under what circumstances to hide it.
Calltip widget: Add a new 'app' attribute to it

- This is used to hold QtCore.QCoreApplication.instance() because QtGui.qApp
is not returning the current app instance.
Editor: Use the new calltip widget to display signatures
Editor: Improve how to show signatures using the calltip widget

- Fix position where the widget is placed.
- Use the same format as the one of our other calltips.
External Console: Use the new calltip widget to show signatures
Object Inspector: Correctly center intro message using css and making it occupy less horizontal space

- This improves revision 2dc19115a168
Object Inspector: Correctly center no docs warning using css
IPython Console: Correctly center kernel loading message with css
Editor: Improve calltip signature format

- Wrap text at 50 lines.
- Highlight special characters (parenthesis, equal signs, commas) in red.
Editor: Align signature args to the first left parenthesis

- Besides, apply _format_signature to each signature separately.
Editor: Use the same font size and family for calltips as the one used for text

- This way if text size is increased/decreased or its font is changed , calltips
will adjust correctly, instead of remaining at a fixed state.
Calltip widget: Add three more conditions to hide it

1. When the pressing the arrow down key.
2. When clicking on it with the mouse.
3. When clicking anywhere on its parent widget.
External Console: Use the new calltip widget to display signatures
Object Inspector: Make sections bottom border a little bit lighter
Editor/External Console: Improve calltips format

- Make calltip text a bit smaller than its title.
- Make its title to have the same font as the one of the surrounding text.