reflect the removal of GUI redirects in SC

GUI redirects have been removed in SC 3.7alpha. That means e.g. rather
than QKnob being the implementing class and Knob being its
representation independantly from the currently active GUI scheme
(Cocoa, Qt...) Knob is the implementing class and QKnob its subclass
which merely exists for backward compatibility.
If you are using CVCenter under SC 3.7 you should update SC to the
latest commit.

Signed-off-by:  <st9fan@gmail.com>