Updates the TLS and CA certificate sections to use algorithms
better than md5. Using md5 as a digest causes nginx to fail
to load because it is not accepted by open ssl.
Closes#3571
Multiple people within my work organisation were caught out by the fact
that the trusted client cert issuers must be given in a file named
`ca.crt` and that other filenames will fail to work.
This change makes it more clear to those who stumble across the
documentation that this is a potential gotcha.
