Add SHA256 and ECDSA algorithm support to SSHFP

Sample zone file:

    $TTL	1d
    $INCLUDE Kexample.com.+008+18169.key
    $INCLUDE Kexample.com.+008+57699.key 
    @	IN	SOA	ns.example.com. hostmaster.example.com. (
	     	      1		; Serial 
			 604800		; Refresh
			  86400		; Retry
			2419200		; Expire
			 604800 )	; Negative Cache TTL

	IN	NS	ns.example.com.

    host	IN	A	127.0.0.1
    ; RSA with SHA256
	IN 	SSHFP 1 2 a47a814d90307563b1d3341e2ae32b808bfc154b3b25c1b29a3ab4dc0b22d2ed
    ; ECDSA with SHA1
	IN	SSHFP 3 1 7981f9794bdfc1acfa4645580306522673720bde
    ; ECDSA with SHA256
	IN	SSHFP 3 2 41d3f3f725fcfce5cb91540cd82f8f7872e60d481c6a4faad264becc4f65bb95