Introducting soft-proofing and Black Point Compensation, simplify the

CMM at the end of the pipeline + sparse code refactoring
A new BPC checkbutton has been created in 'Preferences/Color Management'
and in the ICM tool. Better hanbling of widget sensitivity of the output
profile / gamma part of the ICM tool.

rtgui/options.h

@@ -260,6 +260,7 @@ public:
     Glib::ustring fastexport_icm_working;
     Glib::ustring fastexport_icm_output;
     rtengine::RenderingIntent fastexport_icm_outputIntent;
+    bool          fastexport_icm_outputBPC;
     Glib::ustring fastexport_icm_gamma;
     bool          fastexport_resize_enabled;
     double        fastexport_resize_scale;