SSL: add TLS-SRP (RFC 5054) cipher suites
SSL: add tests for PSK and SRP ciphers
SSL: enable hash_size values for sha224, sha384 and sha512

Some of the PSK and SRP ciphers default to sha384, this enables
hash_size for that cipher. It also adds sha512 and sha224 to be
prepared for further cipher enhancements.
SSL: add documentation for PSK and SRP ciphers options