v20210308

Do not use this release, it will be superceded by v20210310.

Many improvements to saturation code for elliptic curves, including more efficient sieving and better division of points using division polynomials instead of elliptic log/exp. The latter is still available and has better automatic precision handling. Also improved construction of newforms from an elliptic curve, using more ap (depending on the conductor) to fix normalisation of the modular symbol.