allow to specify how many times we can try to connect to the database at startup

add config options:
db_startup_connection_max_attempts - default 0 (infinite)
db_startup_connection_attempt_delay - delay in seconds between attempts (default 5)

BREAKING CHANGE: WINIX_PLUGIN_INIT plugin message requires to set result status,
you have to set the result status to true (env.res) if your
plugin was initialized correctly, otherwise winix will not start

winixd/db/dbconn.h

@@ -57,7 +57,7 @@ public:
 	void SetConnParam(const std::wstring & host, const std::wstring & hostaddr, const std::wstring & port,
 					  const std::wstring & database, const std::wstring & user, const std::wstring & pass);
 	void Connect();
-	void WaitForConnection();
+	bool WaitForConnection(size_t attempts_max, size_t attempt_delay);
 	void Close();
 	bool AssertConnection(bool put_log = true, bool throw_if_no_connection = true);
 	void SetDbParameters();
@@ -65,6 +65,7 @@ public:
 
 private:
 
+	void LogNoConnection(size_t attempts);
 	void LogConnectionSocket();
 
 	PGconn * pg_conn;