Bytewords/Bytemoji: Use alternating lists for easier error detection.

See the [PGPfone manual](http://web.mit.edu/network/pgpfone/manual/index.html), search for "Stewart's scheme for error detection". We may want to consider also using at least two lists, maybe even three.

Edit: Independent from how many wordlists we use for data bytes, we could introduce one for checksum words that verify all the words that have occurred since the previous checksum word. That way, sender and recipient can choose their best trade-off for the frequency of check words – having to use less words overall, or having to retransmit a shorter sequence in case of an error. They can even vary the frequency based on how important the transmitted segment of data is.