Api update

Small API update + get the main window as a raw pointer like the main document and the main document view. May throw a logic_error if no main window is present, i.e. the application is not in its main loop, you should not catch it and let Vivy crash...

src/VivyApplication.cc

@@ -92,13 +92,10 @@ VivyApplication::getMainWindow() const
     return mainWindowPtr.get();
 }
 
-/*
- * @return the current VivyDocument, or null if there isn't one or if the current document is not a VivyDocument
- */
-VivyDocument *
-VivyApplication::getCurrentVivyDocument() const
+AbstractDocument *
+VivyApplication::getCurrentDocument() const
 {
     if (!mainWindowPtr)
         throw std::logic_error("No main window in the graphic VivyApplication");
-    return dynamic_cast<VivyDocument*>(mainWindowPtr.get()->getCurrentDocument());
+    return mainWindowPtr.get()->getCurrentDocument();
 }