[Feature Request] ECDSA AND RSA support

[patschi]

This is a new GitHub issue referring to #651. While ECDSA is gaining more attraction and use in the web over time, it's still not supported everywhere. Therefore I'm honestly not that big fan of either RSA or ECDSA.

Most server services, including nginx and apache2, includes support for using RSA and ECDSA, depending on the support of the client. ECDSA is preferred, RSA used as an fallback.

Relevant parts:

• nginx: In case of nginx you can simply provide multiple ssl_certificate config settings, one to the RSA c ertificate and one to ECDSA certificate. Same for the private key. nginx takes care about the rest. (Apache2 handles it most likely the same)
• Froxlor: That might be the more interesting part. Most likely there should be a separated column called "type" or so, so either RSA or ECDSA in the end.

I'd really like having this support in Froxlor in the future :) Thanks for the amazing work!