Camera and Lens profiles directories

In "Preferences", added the possibility to define a "Camera profiles directory" and a "Lens profiles directory" as base paths which enable storing relative paths in the .pp3 files.

rtgui/preferences.h

@@ -112,6 +112,8 @@ class Preferences final :
     MyFileChooserButton* darkFrameDir;
     MyFileChooserButton* flatFieldDir;
     MyFileChooserButton* clutsDir;
+	MyFileChooserButton* cameraProfilesDir;
+	MyFileChooserButton* lensProfilesDir;
     Gtk::Label *dfLabel;
     Gtk::Label *ffLabel;