Let's try Effect management once more

As usual, I started out intending to do as little as possible
to this to get it working and wound up going overboard.

However, I believe it does allow easy management of the effects
and this will provide a basis for the full blown plugin manager
dialog.

include/audacity/EffectInterface.h

@@ -81,9 +81,6 @@ public:
    // Whether the effect supports realtime previewing (while audio is playing).
    virtual bool SupportsRealtime() = 0;
 
-   // Whether the effect should be shown in menus right from the start.
-   virtual bool EnableFromGetGo(){ return false;};
-
    // Can the effect be used without the UI.
    virtual bool SupportsAutomation() = 0;
 };