Distinguish in table whether a protocol is "implemented but off by default"

[fingolfin]

E.g. hmac-md5-96 may be in principle available in an implementation, but turned off by default for security reasons. In this case, show it as "Off by default" or "Yes*" (with * hyperlink to a ref), or perhaps add a tooltip. Also, change the color from green to yellow or so?

[fingolfin]

See also #7