This patch introduces the "argv" property to CcPanel. Panels that
wish to handle extra arguments shall override it and act
appropriately in the constructor.
https://bugzilla.gnome.org/show_bug.cgi?id=657093
Instead of settings the absolute value of the repeat rate in msecs
through the scale, we set the number of chars per sec, and
use GSettings' bindings functions to transform those a timeout.
https://bugzilla.gnome.org/show_bug.cgi?id=569612