ENYO-3082: added option to delay tab switch

* ENYO-3082: added option so tab switch request is fired before actual
  switch. The actual switch is triggered by user.

Related JIRA: https://enyojs.atlassian.net/browse/ENYO-3082

Enyo-DCO-1.1-Signed-off-by: Dominique Dumont <dominique.dumont@hp.com>'