Add a set color command

[erni-dan]

Please add to MyCobot.cpp

void MyCobot::SetColor(char red, char green, char blue)
{
    LogTrace;
    std::lock_guard<std::mutex> lock(command_mutex);
    std::function<void()> f = [this, red, green, blue]() {
        QByteArray command(CommandSetLedRgb);
        command += static_cast<char>(red);
        command += static_cast<char>(green);
        command += static_cast<char>(blue);
        command += FIRMATA_FOOTER;
        SerialWrite(command);
    };
    commands.push_back(std::make_pair(Command::SetLedRgb, f));
}