Adds -vv flag for "very verbose".
Includes estimated message size when enabled. The size is an estimate because it is the canonical size for the proto message, but not necessarily its actual on-the-wire size.
To better support printing of google.protobuf.Any messages (error details), this
also makes a few other changes:
1. Allows printing of unresolvable Any messages using an "@value" field in JSON output
that has the base64-encoded embedded message data.
2. Improves support for "-format text" to show expanded Any messages if possible.
(Due to limitations in underlying proto package, this will usually *not* be
that helpful. But this should greatly improve with v2 of the go protobuf API.)
3. Addresses a TODO in existing AnyResolver code to lazily fetch descriptors
as needed instead of having to download all files eagerly.
Joshua Humphries