rbt status-update didn't survive some of the changes to commands in

RBTools 3. Attempting to set or get a status update would fail at a few

different points. Mainly these had to do with trying to pass in things the

api_root to functions that no longer took them.
Even with those fixed, this command's invocation was a bit strange. It

worked like a multi-command, but had the action last. This meant that

the entire list of options had to be shared across all subcommands.
This change fixes the broken code paths and, in the meantime, redoes

this as a multi-command.
Each subcommand has its own options that pertain to it, and this allows

us to move some validation into the options themselves. For instance,

the status update ID is now required for delete, but is optional for

the other subcommands.
To support backwards-compatibility, we check at option parsing time if

the last parameter is the action name (indicating an old invocation,

where this had to appear last). If found, we warn and then fix up the

order of arguments.

Tested each subcommand on my dev server, along with each available option.

This includes --review with a JSON document. Every subcommand and option

gave me the results I expected.
Tested the validation of the options that support it.
Tested help output for the main command and all subcommands.