Add support for nickname to TT protocol

mainwindow.cpp

bool MainWindow::parseArgs(const QStringList& args)
{
    ...
    AddLatestHost(entry);
    Disconnect();
    Connect();

    QString nickname = ttSettings->value(SETTINGS_GENERAL_NICKNAME).toString();
    if (nickname.isEmpty()) {
        if (!entry.nickname.isNull()) {
            QByteArray name(entry.nickname.toStdString().c_str(),
                            entry.nickname.toStdString().length());
            nickname = QUrl::fromPercentEncoding(name);
            ttSettings->setValue(SETTINGS_GENERAL_NICKNAME, nickname);
            TT_DoChangeNickname(ttInst, _W(nickname));
        }
    }
    ...
}

------------------------------------------------------------

void MainWindow::slotLoadTTFile(const QString& filepath)
{
    ...
    AddLatestHost(entry);
    Disconnect();
    Connect();

    QString nickname = ttSettings->value(SETTINGS_GENERAL_NICKNAME).toString();
    if (nickname.isEmpty()) {
        if (!entry.nickname.isNull()) {
            ttSettings->setValue(SETTINGS_GENERAL_NICKNAME, entry.nickname);
            TT_DoChangeNickname(ttInst, _W(entry.nickname));
        }
    }
    ...
}