added sha256 and ec-add-modp commands.
allow fetch-stealth to optionally take no arguments (defaults to 0/00000000)
cast_chunk and uncast_type removed from libbitcoin
bugfix: disable reuse_key_option by default in stealth-newkey
clean up long lines in sx help output.
new stealth documentation.
decode_hex_digest is removed from libbitcoin, replace with decode_hash/decode_short_hash instead.