qt: Adds a global option in preferences to use usr_path as the default

open directory for image file selection.

src/qt/qt_progsettings.cpp

@@ -113,12 +113,14 @@ ProgSettings::ProgSettings(QWidget *parent) :
 
     mouseSensitivity = mouse_sensitivity;
     ui->horizontalSlider->setValue(mouseSensitivity * 100.);
+    ui->openDirUsrPath->setChecked(open_dir_usr_path > 0);
 }
 
 void ProgSettings::accept()
 {
     strcpy(icon_set, ui->comboBox->currentData().toString().toUtf8().data());
     lang_id = ui->comboBoxLanguage->currentData().toUInt();
+    open_dir_usr_path = ui->openDirUsrPath->isChecked() ? 1 : 0;
 
     loadTranslators(QCoreApplication::instance());
     reloadStrings();