Use std::is_permutation instead of own algorithm

[xR3b0rn]

E.g. instead of

for (const auto& sig : rhs.Signals())
{
    auto beg = _signals.begin();
    auto end = _signals.end();
    equal &= std::find(beg, end, sig) != _signals.end();
}

That can be used:

equal &= _signals.size() == rhs.Signals().size() && std::is_permutation(_signals.begin(), _signals.end(), rhs.Signals().begin());