Standardize filter curves. Uniform temperature prior.

This release replaces filter transmission functions with generic filter curves from the Spanish Virtual Observatory wherever possible. It also changes the prior on the blackbody temperature from log-uniform to uniform for the purposes of bolometric light curves. Since the previous version, there was a bug in calculating the maximum/minimum validity times for shock cooling models when using an intrinsic scatter parameter, which is now fixed. See other minor changes in release-history.rst.