make file picker contruct using whatever soundfont path is available at construction-time. work towards giving Processor access to change its File on load.

Source/FluidSynthModel.h

@@ -56,6 +56,8 @@ public:
     */
     void removeListener (Listener* listener);
 
+    const String& getCurrentSoundFontAbsPath();
+
 private:
     SharesParams& sharesParams;