For option arguments that must be members of an array, do the
check in the option parsing by providing an array of allowed
option arguments (e.g. vm create -s bad).
Emit better errors for options arguments that should be integers
(e.g. fw add-rule -s/-e), and for regular arguments that should
be integers (e.g. lb create src-port/dst-port).
Include help output in additional cases:
* invalid id formats with slashes
* invalid/duplicate/missing fields used when multiple fields
separated by a comma is allowed
* invalid object references when using post subcommands
* invalid location for list -l option