Initial commit for real hidpi support

Note: This commit has only been tested on MacOS

Changes:
- Icons now use the native hidpi support from Gtk (through Icon Theme)
- Icons are now directly generated from scalable file (i.e. SVG file)
- Widget sizes are scaled based on DPI and scale factor
- Font size is scaled based on DPI and scale factor

rtgui/profilepanel.h

@@ -62,8 +62,8 @@ private:
     Glib::ustring storedValue;
     Glib::ustring lastFilename;
     Glib::ustring imagePath;
-    RTImage *profileFillModeOnImage;
-    RTImage *profileFillModeOffImage;
+    const Glib::ustring modeOn, modeOff;
+    RTImage* const profileFillImage;
     Gtk::ToggleButton* fillMode;
     Gtk::TreeIter currRow;
     ProfileStoreEntry *lastSavedPSE;