interpolation and query_disc should use verify_angles

[mweastwood]

seeing weird results when phi < 0.

[mweastwood]

also interpolate should look more like

template <typename T>
T interpolate(int nside, int order, T* pixels, double theta, double phi)
{
    auto map = construct_healpix_map(nside, order, pixels);
    auto ptg = pointing(theta, phi);
    return map.interpolated_value(ptg);
}