code gen: use the handler field

[tjayrush]

We have a field called handler in the command line data.

Currently, we use it to order the handlers in the output.go file, but it can be used elsewhere. It actually could serve as an "importance" marker and be used to order two other things:

1. The help text
2. The API documents

The sort order would be:

order by handler then order in list of commands.

Currently for the two things mentioned above we only order by the item's order of appearance in teh data file.