[skip ci] support of style sheet in branding framework

src/App/Branding.cpp

@@ -44,6 +44,7 @@ Branding::Branding()
     filter.push_back("WindowIcon");
     filter.push_back("ProgramLogo");
     filter.push_back("ProgramIcons");
+    filter.push_back("StyleSheet");
 
     filter.push_back("BuildVersionMajor");
     filter.push_back("BuildVersionMinor");

src/Gui/Application.cpp

@@ -2065,6 +2065,13 @@ void Application::runApplication(void)
     mdi->setProperty("showImage", hGrp->GetBool("TiledBackground", false));
 
     std::string style = hGrp->GetASCII("StyleSheet");
+    if (style.empty()) {
+        // check the branding settings
+        const auto& config = App::Application::Config();
+        auto it = config.find("StyleSheet");
+        if (it != config.end())
+            style = it->second;
+    }
     if (!style.empty()) {
         QFile f(QLatin1String(style.c_str()));
         if (f.open(QFile::ReadOnly)) {