A small number of related changes.
* Make the default encryption algorithm be Rijndael (AES) rather than
Blowfish. I think this is now the right recommendation to make,
even if it's not my personal taste. (I'm actually using Twofish
nowadays anyway.)
* Make the default field size for Schnorr groups be 3072 bits rather
than 2048, which reflects the advice given by NIST and IEEE 1363.
* Reformat the tripe-keys.master file in line with current thinking.
* Fix a minor typo in tripe-keys.conf.5.in.