* Correct list's "find" and "get" blocks help.
Both blocks were using the same help URL.
Two unrelated results of recompiling messages:
* Allow unwanted 'qqq' messages to be reverted.
* 'constants.json' is unchanged, but sorted.
Also improve python json dumping.
Our files are up to a decade old, and have churned so much, that the initial author of the file no longer has much meaning.
Furthermore, this will encourage developers to post to the developer group, rather than emailing Googlers (usually me) directly.
