Parameter info tables should include the `required` flag

[nightroman]

Parameter info tables should include the required flag:

ParameterName = @{
    description = 'Description.'
    default = 'Default value.'
    wildcard = $true|$false
    required = $true|$false
}

The Mandatory attribute automatically converted into required="true" is not enough. A required parameter is not always mandatory. Sometimes it is better to omit Mandatory (e.g. to avoid useless prompts and write useful errors instead).