Consider switching default from RSA to EC

[TinCanTech]

While switching default from RSA to EC is probably a little too intrusive, making it easier to setup easyrsa to use EC-by-default on a given PKI is simple and useful.

eg:

easyrsa init-pki-ec

Which would pre-configure EASYRSA_ALGO=ec and EASYRSA_CURVE=secp384r1.

Allowing cascading vars files, so that the PKI vars file always comes first and then one other Global vars file can be sourced, appears to be suitable.