Description of problem:

help should specify possible values for enumerables:
For example when running "help add vm" there are few parameters which require specific values : e.g os-type ,  same is true for --cpi-id for add cluster or sorage-type for add datacenter . 
It would be nice if help will contain the possible values for those enumerables. 


Version-Release number of selected component (if applicable):


How reproducible:


Steps to Reproduce:
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Actual results:


Expected results:


Additional info:

help add vm 

USAGE
  
  add <type> [base identifiers] [attribute options]
  
DESCRIPTION
  
  Creates a new object or adds existent with type vm. See 'help add' for generic
  help on creating objects.
  
ATTRIBUTE OPTIONS
  
  The following options are available for objects with type vm:
  
    * --name: string
    * --template-id|name: string
    * --cluster-id|name: string
    * [--quota-id: string]
    * [--timezone: string]
    * [--os-boot: collection]
      {
        [boot.dev: string]
      }
    * [--custom_properties-custom_property: collection]
      {
        [custom_property.name: string]
        [custom_property.value: string]
      }
    * [--os-type: string]
    * [--usb-enabled: boolean]
    * [--usb-type: string]
    * [--type: string]
    * [--os-initRd: string]
    * [--display-monitors: int]
    * [--display-type: string]
    * [--display-allow_override: boolean]
    * [--os-cmdline: string]
    * [--cpu-topology-cores: int]
    * [--memory: long]
    * [--high_availability-priority: int]
    * [--high_availability-enabled: boolean]
    * [--domain-name: string]
    * [--description: string]
    * [--stateless: boolean]
    * [--cpu-topology-sockets: int]
    * [--placement_policy-affinity: string]
    * [--placement_policy-host-id|name: string]
    * [--origin: string]
    * [--os-kernel: string]
    * [--disks-clone: boolean]