The listSiteRoles() methods list all the roles that can be
      assigned to a member of a site.
  
  
listSiteRoles
listSiteRoles() lists all the roles that can be assigned
        to a member of a site.
      Returns
Returns an array containing strings representing the roles available to assign to a member of a site.
Example
  var roles = siteService.listSiteRoles(); 
      
        The preceding code snippet would return a list of roles such as:
SiteManager SiteCollaborator SiteContributor SiteConsumer
listSiteRoles(shortName)
listSiteRoles(shortName) lists all the roles that can be
        assigned to a member of a site, for a specific site.
      Parameters
- shortName
 - A string representing the short name of the site to list roles for.
 
Returns
Returns an array containing strings representing the roles available to assign to a member of a site.
Example
  var roles = siteService.listSiteRoles("test-site"); 
      
        The preceding code snippet would return a list of roles for the specified site, such as:
SiteManager SiteCollaborator SiteContributor SiteConsumer