acf model parsing edge cases

[headupinclouds]

@xsacha posted:

Even if you name it pcb but the file doesn't exist it will error out ... if you name it .dat and the file doesn't exist (or even if it does), it doesn't error

[headupinclouds]

If you have a file with an unsupported extension then these methods will return false:

    bool good() const { return m_good; }
    explicit operator bool() const { return m_good; }

Asigned here:

Detector::Detector(std::istream& is, const std::string& hint)
{
    m_good = deserializeAny(is, hint) == 0;
}

Detector::Detector(const std::string& filename)
{
    m_good = deserializeAny(filename) == 0;
}