Added support to export certificates in a zip bundle

[jrocha]

Solves issue #392

[TinCanTech]

This is useful but the problem here is: how do you do this for Windows ?

I don't believe Easy-RSA should be compressing your data, that is a job for another tool (Which should also support Windows).

That is only my personal opinion, so I'll leave this for you to decide.

[jrocha]

I think easy-rsa is like swiss knife for certificates. Adding export-zip would be another option in this swiss knife without needing to use another tool like a shell script to get the job done. I hear you regarding running it on Windows. I did not thought about. It would be doable using PowerShell recent versions. Personally, I use easy-rsa under cygwin when I'm on Windows box, so I have zip available. Comments on adding PoweShell (>v5.0) to compress on Windows are welcome.

[TinCanTech]

ecrist likes it #392, so I'll consider this soon.

[TinCanTech]

This style of options: zip_opts="$zip_out $zip_opts $crt_in $key_in" is no longer supported.

Closing this PR.