Distinct button bars for graphical and textual modes

This bit the textual mode plain old text based buttons
and retains the bitmap buttons for graphical mode.

It also allowed me to remove the manual accelerator table 
building (no access keys in GUI mode) which was a good 
thing as I really didn't know if the was gonna work for
non-English keyboards anyway.

include/audacity/EffectInterface.h

@@ -158,6 +158,7 @@ public:
 
    virtual void SetUIHost(EffectUIHostInterface *host) = 0;
    virtual bool PopulateUI(wxWindow *parent) = 0;
+   virtual bool IsGraphicalUI() = 0;
    virtual bool ValidateUI() = 0;
    virtual bool HideUI() = 0;
    virtual bool CloseUI() = 0;