GetMarcherSizeAndOffset could be more efficient with ranges and grabbing all the marchers info

[rmpowell77]

This:

auto AnimationView::GetMarcherSizeAndOffset() const -> std::pair<wxPoint, wxPoint>
{
    auto mode_size = towxPoint(mView->GetShowFieldSize());
    auto bounding_box_upper_left = mode_size;
    auto bounding_box_low_right = towxPoint({ 0, 0 });

    for (auto i = 0; mAnimation && i < mView->GetNumPoints(); ++i) {
        auto position = towxPoint(mAnimation->GetAnimateInfo(mCurrentBeat, i).mMarcherInfo.mPosition);
        bounding_box_upper_left = wxPoint(std::min(bounding_box_upper_left.x, position.x), std::min(bounding_box_upper_left.y, position.y));
        bounding_box_low_right = wxPoint(std::max(bounding_box_low_right.x, position.x), std::max(bounding_box_low_right.y, position.y));
    }

    return { bounding_box_low_right - bounding_box_upper_left, mode_size / 2 + bounding_box_upper_left };
}

Looks like it could be done with ranges more efficiently.