GH-338, GH-513, GH-700 Unify edit instance with console window

* The resulting instance window can be closed at any point.
* Main window is kept open and running instances are marked with a badge.
* Multiple instances can now run from the same MultiMC - it's even more **multi** now.
* MultiMC can be entirely closed, keeping Minecraft(s) running.

application/MainWindow.h

@@ -37,6 +37,7 @@ class MinecraftLauncher;
 class BaseProfilerFactory;
 class GroupView;
 class ServerStatus;
+class InstanceWindow;
 
 class MainWindow : public QMainWindow
 {
@@ -54,6 +55,8 @@ public:
 	void checkSetDefaultJava();
 	void checkInstancePathForProblems();
 
+	InstanceWindow *showInstanceWindow(InstancePtr instance, QString page = QString());
+
 private slots:
 	void onCatToggled(bool);
 
@@ -159,6 +162,8 @@ private slots:
 	 */
 	void downloadUpdates(GoUpdate::Status status);
 
+	void on_instanceWindowClose();
+
 private:
 	void setCatBackground(bool enabled);
 	void updateInstanceToolIcon(QString new_icon);
@@ -195,4 +200,7 @@ private:
 
 	// managed by the application object
 	Task *m_versionLoadTask;
+
+	// map from instance ID to its window
+	QMap<QString, InstanceWindow *> m_instanceWindows;
 };