a speech on it by Mufti Zahid Hussain al-Qadiri http://thesunniway.com/speeches/mufti-zahid-hussain-qadri/360-ikhtiyaraat
someone correct me if i'm wrong but i think it is the belief that the prophet [peace be upon him] is the deputy of Allah and he has been given power to do as he wishes.
What does Ikhtiyar al-kull mean? I've seen some references to it in Alahazrat's poetry, but I don't know if he has written a treatise on the topic.