GApplication now has a palette. This palette contains all the system
theme colors by default, and is inherited by a new top-level GWidget.
New child widgets inherit their parents palette.
It is possible to override the GApplication palette, and the palette
of any GWidget.
The Palette object contains a bunch of colors, each corresponding to
a ColorRole. Each role has a convenience getter as well.
Each GWidget now has a background_role() and foreground_role(), which
are then looked up in their current palette when painting. This means
that you no longer alter the background color of a widget by setting
it directly, rather you alter either its background role, or the
widget's palette.
With this patch, CEvents no longer stop at the target object, but will
bubble up the ancestor chain as long as CEvent::is_accepted() is false.
To the set accepted flag, call CEvent::accept().
To clear the accepted flag, call CEvent::ignore().
Events start out in the accepted state, so if you want them to bubble
up, you have to call ignore() on them.
Using this mechanism, we now ignore non-tabbing keydown events in
GWidget, causing them to bubble up through the widget's ancestors. :^)
This changes the behavior of the "is_checkable" flag on GAbstractButton
to only be about user interaction checkability. In other words, it now
only prevents the user from checking/unchecking the button, the code.
