Implement Lubich convolution quadratures

[alexfikl]

This fixes the convolution quadratures (hopefully).

TODO:

• Fix using the convolution weights to compute a RL integral.
  • Should be able to integrate $1$ (an overwhelmingly smooth function) to the specified order.
• Fix using the starting weights to correct a RL integral.
  • Should be able to integrate something less smooth at the origin as well.
• Implement the $p$-BDF methods from https://doi.org/10.1137/0517050.
  • Should be able to solve an FODE like in https://doi.org/10.1080/01630563.2012.706673