Protobuf string type should be treated as a Python unicode string usable
in both Python 2.x and Python 3.x. Since we are now using unicode strings,
force encoding as utf-8.
Protobuf bytes type should be treated as a Python byte string. Use hex
values in byte literal even for printable characters, for a better UX.
escapeString() is no longer being used, but has been retained in the
code.
