Reduce include dependences in GUI; break cyclic dependence between View and Model

• renamed directories from plural to singular (Views->View, Utils->Util, etc etc)
• made GUI/Model independent of GUI/View
• organized GUI/Model into subdirectories
• moved GUI/main to App
• moved files from GUI/View to GUI/View/Toplevel
• broke most cyclic dependences between subdirectories of GUI/View (the remaining ones are mostly for calling functions from ProjectManager that should be moved down to ProjectDocument)
• obtained two subdirectories of GUI/Model with non-cyclic dependences (Component, IO); all other subdirectories still forming a big interdependent cluster
• removed some unused source files
• removed numerous unneeded includes
• corrected a few relative include paths
• splitted several source pairs into two pairs
• splitted class Application into two (ApplicationSettings vs SessionData)
• renamed many namespaces
• shuffled code in several functions to treat anomalous conditions first; no else after return
• substituted QWidget::parentWidget for m_mainWindow and other self-made solutions
• converted SavePlotAssistant from class to namespace
• moved some enum definitions to low-level file ID.h

GUI/Utils/Path.h

@@ -38,10 +38,4 @@ QString createUuid();
 
 } // namespace GUI::Util::Path
 
-inline std::ostream& operator<<(std::ostream& stream, const QString& str)
-{
-    stream << str.toStdString();
-    return stream;
-}
-
 #endif // BORNAGAIN_GUI_UTILS_PATH_H