track point count with more than 65535 points

[Régis ROY]

on GT600, device can store up to 262000 points. I think CountCommand (in commands.cpp) should use first byte of the response as the highest order 8 bits of a 24bit values. Code could look like this:

QByteArray CountCommand::sendAndReceive()
{
    // TODO: what is the first byte?
    const QByteArray result = IgotuCommand::sendAndReceive();
    if (result.size() < 3)
        throw IgotuError(IgotuCommand::tr("Response too short"));
    count = qFromBigEndian<quint16>(reinterpret_cast<const uchar*>
            (result.data() + 1));
    count += result.data()[0]<<16;
    ...