merge doublemelon (#2067)

non-exhaustive (but exhausting) list of changes:

* base laid for multiple window support, but will likely require more work to work correctly
* encapsulation of frontend state for proper multi-instance support
* (JIT still needs a fix for the NDS::Current workaround but we can get there later)
* new, more flexible configuration system

src/frontend/qt_sdl/TitleManagerDialog.h

@@ -41,6 +41,8 @@ namespace Ui
 class TitleManagerDialog;
 class TitleImportDialog;
 
+class EmuInstance;
+
 class TitleManagerDialog : public QDialog
 {
     Q_OBJECT
@@ -94,6 +96,8 @@ private slots:
     void onExportTitleData();
 
 private:
+    EmuInstance* emuInstance;
+
     melonDS::DSi_NAND::NANDMount nandmount;
     Ui::TitleManagerDialog* ui;