added option to not copy screenshots

+ moved select all checkbox to top row, centered.

Signed-off-by: Marcelo Hernandez <marcelohdez.inq@gmail.com>

launcher/ui/dialogs/CopyInstanceDialog.h

@@ -54,6 +54,7 @@ slots:
     void on_copyShaderPacksCheckbox_stateChanged(int state);
     void on_copyServersCheckbox_stateChanged(int state);
     void on_copyModsCheckbox_stateChanged(int state);
+    void on_copyScreenshotsCheckbox_stateChanged(int state);
 
 private:
     void checkAllCheckboxes(const bool& b);