This provides descriptions for all commands. Command help now
uses the following format:
```
DESCRIPTION
Usage:
BANNERS
Commands:
COMMAND DESCRIPTION
Post Commands:
COMMAND DESCRIPTION
Options:
OPTION DESCRIPTION
Post Options:
OPTION DESCRIPTION
```
This required substantial changes to rodish, so this updates to the
current head of rodish.
Other minor changes:
* Use "virtual machine" instead of "VM" in command help
* Use "command" or "post-command" instead of "subcommand" in usage
* Use "ps-id" instead of "subnet-id" in {at,de}tach-subnet command usage
* Use "rule-id" instead of "id" in delete pg firewall rule usage
* Use "md-id" instead of "id" in delete pg metric destination usage
* Avoid literal "Usage: " in help -u output
355f7d3f97