WebUI: Allow to retrieve qBittorrent version

New GET method:
 * version/qbittorrent: qBittorrent version

Closes #1872.

src/webui/requesthandler.cpp

@@ -108,6 +108,7 @@ QMap<QString, QMap<QString, RequestHandler::Action> > RequestHandler::initialize
     ADD_ACTION(command, recheck);
     ADD_ACTION(version, api);
     ADD_ACTION(version, api_min);
+    ADD_ACTION(version, qbittorrent);
 
     return actions;
 }
@@ -225,6 +226,11 @@ void RequestHandler::action_version_api_min()
     print(QString::number(API_VERSION_MIN), CONTENT_TYPE_TXT);
 }
 
+void RequestHandler::action_version_qbittorrent()
+{
+    print(QString(VERSION), CONTENT_TYPE_TXT);
+}
+
 void RequestHandler::action_command_shutdown()
 {
     qDebug() << "Shutdown request from Web UI";

src/webui/requesthandler.h

@@ -83,6 +83,7 @@ private:
     void action_command_recheck();
     void action_version_api();
     void action_version_api_min();
+    void action_version_qbittorrent();
 
     typedef void (RequestHandler::*Action)();