This adds complexity but will save a lot of bandwidth, as most of the
strings and byte arrays we want to send are less than 128 bytes.

The extra complexity isn't exposed outside of the serial component.

The invitation and private messaging UIs are currently broken. Some key
rotation bugs were fixed; others may have been created (unit tests
needed). An encoding for private keys was added. Pseudonyms were moved
out of the messaging package and ratings were moved in.