horizon: Add SSL protocol option.

[OttoHollmann]

Current setting in cookbook templates exclude only SSLv2 and SSLv3. SSLProtocol all -SSLv2 -SSLv3 but in these days TLSv1.0 protocol is already deprecated, so it will be nice to have any option how to disable this old protocol. We can add protocol option (this PR) and keep it up to user to select which protocol he wants, disable TLSv1.0 in default settings or both of them.