refactor to let request-cert and selfsign-cert use different hashes
refactor to let request-cert and selfsign-cert use different hashes

namely sha1 and sha512 as well with sha256 as default

akgood/yubico-piv-tool,hirden/yubico-piv-tool,akgood/yubico-piv-tool,akgood/yubico-piv-tool,Yubico/yubico-piv-tool,hirden/yubico-piv-tool,ato/yubico-piv-tool,Yubico/yubico-piv-tool,Yubico/yubico-piv-tool,ato/yubico-piv-tool,akgood/yubico-piv-tool