work on settings (set and show), perf improvement when adding row into table

settings.cpp

@@ -20,11 +20,20 @@ std::string Settings::date_to_string(long date) {
 	return ::date_to_string(date, get_setting("DATE_FORMAT"));
 }
 
-std::basic_string<char> Settings::get_setting(const std::string &name) {
+std::string Settings::get_setting(const std::string &name) {
 	for(const auto& pair : m_settings) {
 		if (pair.first == name) return pair.second;
 	}
-	// TODO exception
+	throw Exception("unsupported setting name: " + name);
+}
+
+void Settings::set_setting(const std::string &name, const std::string &value) {
+	for (auto it = begin(m_settings); it != end(m_settings); ++it) {
+		if (it->first == name)  {
+			*it = std::make_pair(name, value); 
+			return;
+		}
+	}	
 	throw Exception("unsupported setting name: " + name);
 }