This doesn't affect the text output, which was already using a
stringified name.  The earlier stringification does change the JSON
output from an enumeration integer (e.g. 2) to the string form
(e.g. "File").  If/when we transition to Merkle-object types named by
their hash, we will probably want to revisit this and pass both the
type hash and human-readable-but-collision-prone name on to clients.

License: MIT
Signed-off-by: W. Trevor King <wking@tremily.us>