allow passing custom openssl opts

[n11c]

This PR introduces a way to pass custom arguments to openssl for the gen-req, sign-req and build-ca subcommands. It basically handles a new "--" argument where everything after it is passed unchanged to openssl

[n11c]

Note: the motivation behind this is roughly the same as PR #62 although it is more generic and could be used for other use cases

[funkypenguin]

Came here to commit a similar PR, permitting passing extra openssl arguments via an environment variable. My implementation (for my needs) permits passing of custom arguments for generating CAs, signing, revoking, and generating CRL. May I suggest you extend your implementation to cover revoking and gen-crl?

[TinCanTech]

Sorry. This is simply not going to be supported by EasyRSA.

Use openssl directly for such use.

If any particular use can be integrated into easyrsa then please submit PRs on a single use case.