add apply button to the settings dialog (bug #44081) * main-window.cc (process_settings_dialog_request) connect signal for applying the changes, settings dialog is non modal now; (request_reload_settings): new slot for siganl from settings dialog when when apply button was clicked * main-window .h: new slot request_reload_settings * settings-dialog.cc (constructor): connect signal when button box is clicked to the new slot button_clicked; (button_clicked): new slot * settings-dialog.h: new signal and related slot * settings-dialog.ui: new applay button