v0.25.0

A few small updates since RC2. Lots of new stuff in this release, take a look at the RC1/RC2 release notes for details.

• Relax strictness for complete standard fens in uci and opening books. Fen
  must still be standard, but default values will be substituted for sections
  that are missing.
• Restore some backwards compatibility in cudnn backends that was lost with
  the addition of the new convolution implementation. It is also on by default
  for more scenarios, although still off for fp16 on RTX gpus.
• Small logic fix for nps smoothing in the new optional experimental time
  manager.