added basic support for htmx (ajax)

- if there is HX-Request header present we sent only a part of the whole html
- we return only specific stream defined by [out ...] ezc statement
- the name of the stream is passed in the 'frame' parameter
  (if not present then 'content' is assumed)
- added ezc function: winix_is_htmx_request

winixd/core/app.h

@@ -164,6 +164,7 @@ private:
 	std::wstring http_header_name;
 	std::wstring http_header_value;
 	std::string http_header_8bit;
+	std::wstring empty_response;
 
 	morm::ModelConnector model_connector; // main thread model connector, each thread has its own connector
 	morm::JSONConnector json_connector;
@@ -206,6 +207,7 @@ private:
 	void SaveSessionsIfNeeded(); // !! IMPROVE ME wywalic do menagera sesji??
 	void LogAccess();
 	void SendData(const BinaryPage & page, FCGX_Stream * out);
+	const std::wstring * CreateFrameAnswer();
 	void CreateJSONAnswer();
 
 	void ReadRequest();