closes#553
* rename flat to encode
* rename unflat to decode
* alias both to their old names
* both only print to stdout
use can pipe to file
* split cbor and hex flags
* hex flag works for either cbor or flat
* encode takes --to flag
[name, named-debruijn, debruijn]
* decode takes --from flag
[name, named-debruijn, debruijn]