message: Do not have the main lumina-pdf window grab the keyboard.
  This breaks the consistency of keyboard shortcuts between presentation mode and normal viewing, but the up/down arrows will properly scroll the window now if a partial-page view mode is selected.
diff: @@ -94,7 +94,6 @@ MainUI::MainUI() : QMainWindow(), ui(new Ui::MainUI()){
  //Now set the default state of the menu's and actions
  ui->menuStart_Presentation->setEnabled(false);
  ui->actionStop_Presentation->setEnabled(false);
  - this->grabKeyboard();
  }
  MainUI::~MainUI(){
  