This makes loading faster, with less I/O, avoids unnecessary
code duplication (around 1k lines shaved), and ensures that
all the panels link and work appropriately.
By the same token, it will stop external panels from being
created, and loaded.
https://bugzilla.gnome.org/show_bug.cgi?id=690036
So it's possible to switch directly to a section of the shortcuts
tab, rather than have users look for particular sections when redirected
there through a link.
https://bugzilla.gnome.org/show_bug.cgi?id=684280
To make this work, we need to move the setting up of priv->builder
to the instance init, so that it is available when construct properties
are set; the other setup needs to remain in the constructor, since
it relies on construct properties.
https://bugzilla.gnome.org/show_bug.cgi?id=662489
Use a constructor so that the "shell" property is already set.
This allows use to block accels from working when capturing a key,
as well as parent dialogues properly for the toplevel.
