Add support and set defaults for following in default sshd config:

* Ciphers:		aes256-ctr, aes192-ctr, aes128-ctr

* HostKeyAlgorithms:	ssh-dss, ssh-rsa, ecdsa-sha2-nistp521,
			ecdsa-sha2-nistp384,ecdsa-sha2-nistp256

* HostKeyFiles:		default is empty

* KexAlgorithms:	diffie-hellman-group-exchange-sha256,
			diffie-hellman-group14-sha1,
			ecdh-sha2-nistp521,ecdh-sha2-nistp384,
			ecdh-sha2-nistp256